Resonance Pre-foundation
Programmes
(PCCP) Division
Career Care
COURSE : KVPY (STAGE-) I
BIOLOGY
WORKSHOP TAPASYA
SHEET
© Copyright reserved.
All right reserved. Any photocopying, publishing or reproduction of full or any part of this study material is strictly
prohibited. This material belongs to only the enrolled student of RESONANCE. Any sale/resale of this material is
punishable under law. Subject to Kota Jurisdiction only.
Subject : Biology
KVPY
S. No.
Topics
Page No.
1.
Genetics & Evolution
1 - 17
Reproduction
18 24
25 33
4
Microorganisms & Diseases
34 41
.
2.
-
3.
Control & Coordination
-.
-5
Control & Co-ordination
42 - 48
Transmission of traits from one generation to another generation is known as heredity. These characters are fixed for a particular individual.
VARIATIONS
It is concerned with the differences between the individuals of same species and also between the offsprings of the same parents.
Variations could be of two types :
(i) Somatic Variation (ii) Germinal Variation
(i) Somatic Variation : It affects the somatic cells of an organism. It is neither inherited from parents nor transmitted to next generations. It is acquired by individuals during their life and is lost with death. So it is called as acquired variation.
[ Somatic variations are due to :
(a) Environment (b) Use and disuse of organs (c) Conscious efforts
(ii) Germinal Variation : This variation affects the germ cells of an organism and is consequently inheritable, it is received by the individual from the parents and is transmitted to the next generation.
[ Significance of Variations :
1. Variation enables the organisms to adapt themselves to the changing environment.
2. It forms raw material for evolution.
3. It enables the organisms to face the struggle for
existence in a better way.
4. Helps in improving the races of useful animals and plants.
5. It is the basis of heredity.
6. It also leads to the occurrence of new traits.
TERMS USED IN GENETICS
(i) Gene : Basic unit of inheritance, located on a chromosome. Mendel had used the term ‘factor’ for it
before ‘genes’ were identified.
(ii) Allele : Alternative form of a gene; there are two alleles of a gene which govern the expression of a pair of contrasting character. For example, blue colour and black colour of eyes are two alleles of the eye colour gene.
(iii) Phenotype : The physical or external appearance of an organism, regardless of its genetic constitution. For example, tall and dwarf plants, smooth and wrinkled seeds.
(iv) Genotype : The genetic constitution of an organism. (v) Monohybrid cross : A cross (hybridization experiment) in which a single pair of contrasting character is studied at a time. For example, a cross involving tall and dwarf plant is a monohybrid cross. (vi) Dihybrid cross : A cross involving two pairs of contrasting characters. For example, a cross involving round and yellow seeded plant with wrinkled and green seeded plants.
(vii) Pure-breeding : Characteristics that appear unchanged generation after generation.
(viii) F1 generation (First filial generation) : The offspring produced by the parental generation. (ix) F2 generation (Second filial generation) : The offspring produced by the F1 generation.
(x) Dominant characteristic : Any characteristic that appears in the F1 generation offspring from a cross between parents possessing contrasting characteristics such as tallness and dwarfness in pea plants.
(xi) Recessive characteristic : Any characteristic present in the parental generation that does not appear in the F1 generation but reappears in the F2 generation. (xii) Homozygous : A condition in which the two members of an allelic pair are similar in a diploid organism.
(xiii) Heterozygous : A condition in which two members of an allelic pair are dissimilar.
(xiv) Offspring : Organism produced as a result of sexual reproduction; same as progeny.
(xv) Pedigree : Ancestral record of an organism. (xvi) Back Cross : When F1 individuals are crossed with one of its parents either dominant or recessive, the cross is called back cross.
(xvii) Test Cross : When F1 individuals are crossed with its pure recessive parent, the cross is called test cross. The result of it is always 1:1.
MENDEL’S EXPERIMENT AND LAWS OF INHERITANCE
Gregor Johannan Mendel is called as Father of genetics. With the help of his experiments on garden pea, he was able to formulate laws which explain the manner of inheritance of characters. Mendel’s work
was not recognized at that time, in 1900, Mendel’s laws
were rediscovered by three different scientists :
HEREDITY & EVOLUTION
(a) Hugo de Vries- Holland (b) Karl Correns-Germany (c) Eric von Tschermark-Austria
[ Mendel chose garden pea as plant material for his experiments, since it has following advantages :-1. Well defined characters
2. Bisexual flowers
3. Predominantly self - pollination 4. Easy hybridization
5. Cross fertilization is possible
[ Traits Choosen By Mendel For His Experiment :There are seven traits choosen by Mendel for his experiments
S.No. Characters Dominant Recessive
1 Plant size Tall (T) Dwarf (t)
2 Shape of seeds Round (R) Wrinkled (r)
3 Colour of seed Yellow (Y) Green (y)
4 Colour of flower Violet (V) White (w)
5 Shape of pod Inflated (I) Constricted (i)
6 Colour of pod Green (G) Yellow (g)
7 Position of flower Axillary (A) Terminal (a) Seven Pairs of Contrasting Traits of Garden Pea Studied by Mendel
[ Crossing Technique Employed By Mendel : 1. Selection of Parents
2. Formation of pure line by self pollination. 3. Emasculation (Removal of anther).
4. Bagging (protection from undesired pollination) 5. Pollination (By dusting pollens)
6. Obtaining seeds.
[ Results of Mendel’s Experiments :W hen self pollination was made and F1 generation was obtained, it was found that the resultant generation would express only one of the trait and not the other. The trait which is
being expressed is called as dominant, where as the one which is not expressed is called as recessive trait. In the F
1 generation obtained by self pollination, the dominant and the recessive traits obtained were in the ratio 3 : 1, i.e., 75% of the offsprings which appeared in F2 generation had dominant trait, while 25% had recessive trait.
This ratio 3 :1 is also known as Mendelian Monohybrid ratio.Mendel further found that the phenotypic ratio of 3 : 1 of dominant to recessive form of a trait was actually a genotypic ratio of 1 : 2 : 1 of pure dominant, hybrid & pure recessive forms. The trait which remained hidden in F1 generation got expressed in F2 generation. This was later on proved in F2 generation.
T t i.e. 1 TT 2 Tt 1 tt T TT Tall Tt
Tall 3 tall 1 short
t Tt Tall tt short Gametes from one parent Gametes from other parent
[ Dihybrid Cross : Mendel also performed dihybrid crosses. A dihybrid cross is a cross between two sets of plants involving two pairs of contrasting characters.
For example, a cross between plants having yellow and round seeds (YYRR) with plants possessing green and wrinkled seeds (yyrr) is a dihybrid cross.
P generation
Yellow and round X Green and wrinkled
Seeds (YYRR) Seeds (yyrr)
F1 generation Yellow and round seeds (YyRr)
Selfing
Ratio F2 generation Yellow round (YR) 9
Yellow wrinkled (Yr) 3 Green round (yR) 3 Green wrinkled (yr) 1
16
9 : 3 : 3 : 1 phenotypic ratio in the F2 generation is obtained in a dihybrid cross, and is called the Dihybrid ratio. If we analyse the result of a dihybrid cross, two additional combinations (yellow and wrinkled seeds and green and round seeds) are obtained. It means that yellow/green seed character and round/wrinkled seed character are independently inherited. In other words, the inheritance of one pair is not affected by the presence of the other (also termed as the law of independent assortment). yr yr YR YyRr YyRr YR YyRr YyRr YYRR YR YR yyrr yr yr
×
GametesAll F1 plants are yellow and round seeded
YR YyRr YR Yr yR yr YyRr YR Yr yR yr × YR Yr yR yr Gametes YYRR YYRr YyRR YyRr Yr YYRr YYrr YyRr Yyrr yR YyRR YyRr yyrr yyRr yr YyRr Yyrr yyRr yyrr Genotypic Ratio is 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1
[ Mendel’s Laws Of Inheritence :
1. The principle of Dominance :- When two homozygous individuals with one or more sets of contrasting characters are crossed, the characters that appear in
the F
1 hybrids are dominant characters and those which do not appear in F1 are recessive characters. 2. The principle of Segregation :- [Law of purity ofgametes] :- The law of segregation states that when a pair of contrasting factors or genes or alleles are brought together in a heterozygous condition, the two remain together without being contaminated but when gametes are formed from them the two separate out from each other. This is also known as Mendel’s first
law of heredity.
3. The principle of Independent Assortment : If the inheritance of more than one pair of characters is
studied simultaneously, the factor or genes for each pair of characters assort out independently. It is known as Mendel’s second law of heredity.
MENDELIAN INHERITANCE IN HUMAN BEING
In humans, most of the traits are controlled by dominant genes. However, traits like albinism are due to recessive genes. In an albino human, the homozygous recessive allele causes defective pigmentation. Now, if we consider the inheritance of blood groups in humans, different situation exists. Only two alleles exist for pea character that Mendel studied, but most genes actually exist in population in more than two allelic forms. The ABO blood can occur in any one organism.
Table : Some Common Hereditary Characteristics in Humans
S.No. Character studied Dominant Recessive
1. Eye colour Brown Blue
2. Hair Curly Straight
3. Eye brows Bushy Thin
4. Tongue Rolling Non-rolling
5. Ear lobe Free Attached
6. Lips Thick Thin
7. Colour vision Normal Colour blind
GENE
• The term ‘gene’ was introduced by Johanssen for
Mendelian factor.
• Chemically gene is formed of DNA
• Genes are transmitted from parents to their offsprings generation after generation.
• Genes are located on chromosomes on locus.
[ Genes have been classified into different categories. (i) Constitutive or house keeping genes : These are those genes which are always in action because their products are always required for cellular activities e.g.,
ATP–ase, enzymes of glycolysis.
(ii) Non costitutive genes are those genes which can be switched on or off as per requirements .
(iii) Split genes : In eukaryotic cells coding bases are not continuous but are interrupted by noncoding sequence, the two are respectively called exons and introns.
(iv) Operons : These are segments of genetic material which function as regulated units or units which can switched on and switched off.
(v) Jumping genes (Transposons) : These are discovered by Mc Clintock (1951) in Maize.
These are those DNA segments which can pass from one place to another in the genome.
STRUCTURE OF DNA
DNA was first isolated by Frederick Meisher (1869) from the pus cells. He named it as nuclein. The structure of DNA was proposed by Watson, Crick and W ilkins in 1953. The model, proposed by these scientists is called ‘Double Helical model’. It is the
best accepted model of DNA.
(i) According to this model, DNA is a large polymer. Its
(ii) A deoxyribo-nucleotide consists of three components :
(a) Deoxyribose sugar (C5H10O4), (b) Phosphate group and
(c) Any one nitrogenous base (Any one of the four types of bases - Adenine, Guanine, Cytosine and Thymine). So depending upon the nitrogenous bases, the nucleotides in DNA can be of four types.
Fig : Double Helical Structure of DNA Molecule (iii) The deoxyribo-nucleotides are joined together by phosphodiester bonds and form a polynucleotide chain. These chains have two ends. One end is called
(iv) A DNA molecule has two such polynucleotide chains, which run in opposite or antiparallel direction. (v) One chain runs in 3’ to 5’ direction while other in 5’
to 3’ direction. So the molecule possesses a polarity.
(vi) Two chains are held together by weak Hydrogen bonds, which are established between the opposite complementary bases (A and T, C and G) of the two chains. There are 2 – H bonds between A and T while
3 – H bonds between C and G.
(vii) Two strands, to acquire maximum stability get coiled or twisted to form the characteristic DNA structure. They twist around a central axis.
(viii) Normal distance between the two base pairs is 0.34 nm.
(ix) The distance between each turn of coil is 3.4 nm. (x) The diameter of the DNA molecule is 2 nm. [ RNA has uracil in place of thymine.
[ Chargaff (1949), demonstrated that the ratio of four nucleotides (A, G, T, C) varies from species to species. However, a specific DNA contains equal amount of particular purines and pyrimidines i.e., the amount of A = T and that of G C. This declaration later to be known
as Chargaff’s rule.
[ Central dogma is the path for flow of genetic information from DNA to m-RNA by the process of transcription and then from m-RNA to protein by the process of translation. The term was given by Crick (1958).
DNA Transcription RNATranslation Proteins
One way flor of information (central dogma)
HOW DO THESE TRAITS GET EXPRESSED
Mendel proposed the inheritance of traits from parents to offsprings by heredity units called factors.
Johanson (1909) replaced the term ‘factor’ by ‘genes’.Gene is a short segment of DNA present on a
chromosome responsible for the synthesis of a particular protein. It is estimated that there are about 30,000 – 40,000 genes present in a human genome.
A genome is a complete set of chromosomes of a
particular species. Human genome contains 23 chromosomes and genome of Pisum sativum has 7 chromosomes. Each gene is present at a specific position on a chromosome called its locus (plural loci). Genes control traits as explained in chart.
Organism
Cells
Nucleus
Chromosomes (Number is fixed for a species),
14 in Pisum sativum DNA Genes Protein Enzyme Catalyses a particular process to form a product Suppose a hormone is formed from gene T
Controls the trait (Height)
Flow chart Genes control the traits through enzymes There are a large number of genes in an organism. All these are not active all the time. They play different roles under different conditions,
SEX DETERMINATION
However, in most of the higher organisms including human beings, the sex of the individual is largely determined by the genetic constitution. In other words the genes inherited from our parents decide whether baby will be boy or girl. The human species has 23 pairs of chromosomes.
Flow chart Types of Chromosomes
Chromosomes in each human (23 pairs or 46)
Allosomes or sex chromosomes (23 pair or 2) Autosomes (22 pairs or 44)
XY (Males) XX (Females)
If the egg is fertilized by ‘X’ bearing sperm the child will be a girl.
If the egg is fertilized by ‘Y’ bearing sperm the child will be a boy.
Mother Father Parents Genotype Gametogenesis Gametes Progeny Daughter Son
XX
XY
X
X
Y
Y
X
X
XY
XX
Fig : Sex determination in the human being
All eggs are alike (each one X-chromosome), but sperms are either with X- or Y-chromosome (50% of each type).
The type of sperm that fertilizes the egg determines whether the child will be son or daughter
Table : Differences between Autosomes and Allosomes
S.No. Features Autosomes Allosomes
(sex chromosomes)
1. Definition Chromosomes which are not connected with sex determination.
Chromosomes which are connected with sex determination.
2. Similarity Similar in males and females. Dissimilar in males (XY) and females (XX).
3. Number of chromosomes
Generally 44 or 22 pairs in human beings.
Generally less (2 or 23rd pair in human beings).
Table : Differences between diploid and haploid organism
S.No. Features Diploid organisms Haploid organisms
1. No. of sets chromosomes Two One
2. Present in pairs Chromosomes present in pairs. Chromosomes present singly.
3. Meiosis Gametic Zygotic
NON-MENDALISM [ Multiple Allelism :
1. Blood group (ABO) is regulated by multiple alleles in Human beings
2. Multiple alleles are multiple alternative or alleles of the same gene which occur in the population of same species.
A chromosome has only one allele and diploid individuals only two alleles
Types of Blood Groups
Blood Group Genotype Antigen Antibody
A B AB O I I , I iA A A A b I I , I iB B B I IA B i i B A+B Nil a Nil a, b
[ Co-Dominance :In co-dominance, both the genes of
an allelomorphic pair express themselves equally in F1 hybrids. It means a heterozygote for codominant genes exhibits both the characters side by side. e.g. Co-dominance of blood alleles in man.
MUTATIONS
Mutation is a phenomenon which results in alteration of DNA sequences and consequently results in changes in the genotype and the phenotype of an organism. In addition to recombination, mutation is another phenomenon that leads to variation in DNA. One DNA runs continuously from one end to the other in each chromatid, in a highly supercoiled form. Therefore loss (deletions) or gain (insertion/ duplication) of a segment of DNA, result in alteration in chromosomes. Since genes are known to be located on chromosomes, alteration in chromosomes results in abnormalities or aberrations. Chromosomal aberrations are commonly observed in cancer cells. [ Types of mutations : On the basis of causes, mutation
are of two types — Spontaneous mutation and induced
mutation.
(i) Spontaneous mutations : The mutations caused by unknown or indistinct natural causes are included in this category. These can be the result of aberrations in DNA or caused by natural factors like ultraviolet radiations and radioactive radiations. In India spontaneous mutations have been seen in the monozyte belt of Kerala which is a radioactive ore rich area.
(ii) Induced mutations : Induced mutations are artificially created, hence also called artificial mutations.
The mutations caused or induced by the physical or chemical factors like radiations, phenol, mustard gas etc. are included in this category. The agents or factors which cause mutation are called mutagens.
The effective mutations are produced by the changes taking place in the sequence of the nitrogenous bases of genes or DNA. These are called point mutation or gene mutation. Sometimes abnormalities developed at the chromosome level also appear like mutation. These are called chromosomal aberrations.
[ Point mutation or Gene mutation : Gene mutations is considered as molecular basis of mutation. These mutation are expressed by the changes taking place at the level of sequence of nitrogenous bases in DNA. The change in the sequence of nitrogenous base can take place by two methods —
(i) Transitions : These are such base pair replacements where a purine is replaced by another purine and a pyrimidine is replaced by another pyrimidine. A purine base adenine (A) is replaced by guanine (G) or vice versa and a pyrimidine base cytosine (C) is replaced by thymine (T) or vice versa are the examples of transition type of gene mutation.
A G
C T
(ii) Transversions : These are such base pair replacements where a purine base is replaced by a pyrimidine base and vice versa.
Four types of possibilities in transition and eight types in transversion are present in gene mutation.
T C A G Purine Purine Pyrimidine Pyrimidine CHROMOSOMAL ABERRATION
The change in the number & structure of chromosome of an organism is provided with a definite number of genes, which are arranged linearly in a definite manner. Chromosomal aberration may bring about a change in the number or arrangement of the genes. Such changes may produce effect like that of gene mutation. Chromosomal aberrations may be of the following two types.
(a) Numerical chromosomal aberrations : The reduction or increase in the number of chromosomes in an organism is known as numerical chromosomal aberration or variation in chromosome number. It is mainly of two types —
(i) Euploidy : A haploid set of chromosomes (n) in an organism is known as genome. Thus in somatic cells two sets (2n) of genomes are found. Reduction or increase in the number of genomic sets is called euploidy. When the reduction of one full set of genome is there, the monoploids are very less potential. When one, two or more genomic sets are increased in offspring, then they are called polyploids. Polyploids can be triploids (3n, having 3 haploid sets), tetraploids, hexaploids, polyploids and so on. The polyploid crops of potato, groundnut, banana etc. have been found high yielding.
(ii) Aneuploidy : Increase or decrease of one or more chromosomes (not the entire set) is called aneuploidy. Aneuploidy can either be due to loss or addition of one or more chromosomes to the complete set of chromosomes. Aneuploidy is mainly caused by abnormal cell division which results either in repetition or loss of a particular chromosome. Several serious disorders can be developed in human beings due to aneuploidy. Some of them are following.
[ Down’s syndrome : Earlier it was called Mongolian idiocy. It has been find out that repetition of 21st chromosome in the infant is responsible for the development of this syndrome. Such infants have 47 (45 + XY) chromosomes instead of normal 46 (44 + XY) chromosomes. The victim is mentally retarded and shortliving. Since this syndrome is caused by autosomic (21st) chromosome hence these abnormalities are also called autosomal aneuploidy.
[ Patau syndrome : It is caused by repetition of 13 th chromosome.
[ Edward syndrome : It is caused by repetition of 18th chromosome. Such babies can not survive for more than six months.
[ Turner’s syndrome : This syndrome is produced by the deficiency of Y chromosome. The victims have only 45 (44 + X) chromosomes. These are immature, sterile females with underdeveloped genitalia.
[ Klinefelter’s syndrome : This syndrome is developed by the repetition of X chromosomes in a male child. Such infants contain 47 (44 + XXY) chromosomes. These male children are also sterile and have develop enlarged breast in adulthood.
Since Turner’s syndrome and Klinefelter’s syndrome
are the result of aberration of sex chromosomes hence they are also called sex-linked syndromes.
(b) Structural chromosomal aberrations : The abnormalities produced by the break of any segment of a chromosome and often by the rejoining of this segment to another chromosome are called structural show mutagenic effects due to change in the number and arrangement of genes. The structural chromosomal aberrations are mainly of the following
(i) Deletion or Deficiency :The break and loss of a segment of a chromosome is called deletion. The loss is generally by the break of the telomere.
(ii) Duplication : Repetition of a particular segment in a chromosome is called duplication.
(iii) Inversion : The reversal of the sequence of genes in a particular part of chromosome is called inversion. (iv) Translocation : Exchange of a segment of a chromosome between two non-homologous chromosomes is called translocation.
The structural chromosomal aberrations causes several abnormalities in human beings. Some common abnormalities are—
[ Philadelphia 22 : This syndrome is caused by deletion of a segment of 22nd chromosome. The deleted segment rejoins with 9th chromosome. The victim suffers of a type of blood cancer or leukemia. Similarly when a segment of 5th chromosomes transferred to 15th chromosome a symptom called cat cry is developed. The victim infant weeps like a cat. It is also mentally retarded and shortliving.
[ Applications of mutations : By controlled and induced mutation and mediation of biotechnology various useful varieties of animals and plants have been developed. By causing point mutation using gamma radiations the red grained Sonara 64 variety of wheat has been mutated into improved Sharbati Sonara. High yielding polyploid varieties of wheat (5n), potato and coffee (4n), banana (3n) etc. have been developed by the application of chromosomal aberrations. A rust proof variety of wheat has been developed by translocating chromosome segment of wild grass Secale. Some more varieties of crop plants developed by mutation breeding are - NP - 836 of wheat, Hans of peas, Jagannath and HT - 60 of rice, TG - 1 of groundnut.
[ Significance of mutation in organic evolution : ‘Natural
selection’ is considered as the basis of organic
evolution. According to Darwinism the origin of adaptations in any population is by natural selection and any population is adapted to the new atmosphere slowly and gradually. In other words organic evolution is an extremely slow process. Hugo de Vries by his mutation theory proved that a sudden is a well accepted notion that the main source of origin of genetic variations is mutation. The useful and desired variations caused by mutation are naturally selected and thus a new species is originated. Therefore in the act of natural selection and organic evolution mutation plays an important role.
GENETIC DISEASES
Diseases that are transmitted from parents to offsprings are called hereditary or genetic diseases.
( a ) Ha e mophilia :
It is a sex linked hereditary disease. The genes of the
disease are found on sex chromosome-X . Due to this disease blood clots very slow so a patient can die due to excess of haemorrhage. Women acts as carrier only. While in man the recessive gene can be expressed, if present on a X-chromosome. Male Female XY (X) X X Y (X) X X(X) (Vector Daughter) XX (Daughter) (X)Y (Infacted Son) XY (son) ( b ) C o lo ur bl in dn e s s :
This is a sex linked hereditary disease. It's genes are situated on X- chromosomes. In this disease also
women are found as carrier generally and men as patients. A person suffering from colourblindness cannot differentiate between red and green colour. ( c ) Tha la s e mia :
It is a genetic disease that leads synthesis of defective haemoglobin. Blood of patient have to be changed frequently. Cause of this disease is a recessive gene. (d) Sic kle Cell Ana emia :
Cause of this disease is a mutation in gene. In this disease shape of red blood cell becomes sickle like. A child with 50% sickle shaped red blood cells and 50% normal red blood cells can survive and remain anaemic.
EVOLUTION
The term evolution has been derived from the Latin word ‘evolver‘ which meas to unroll. Evolution can be
defined as sequence of gradual development of complex form of life from simple form of life over the course of geological time (millions of year) scale.
S. No. Theory of Evolution Proposed by Special points related to theory 1. Spontaneous Generation/Abiogenesis Theory Aristotle (384 – 322 B.C.)
life comes from living organisms as well as from non-living / organic
matter spontaneously. Eg. Mice from Human sweat, Frog
from Mud etc. 2. Special creation Father Suarez
(1600)
Life is created by God with in 6 days 3. Catastrophism Cuvier (1800) life is continuously created &
destroyed and recreated in different forms. 4. Cosmozoic Richter life reached on earth by cosmic
dust from other planet. 5. Panaspermia Arrhenius life transferred on earth in the form
of spores from other planet.
[ Modern theory or Abiotic theory :
• It was given by A.I. Oparin (1923) and J.B.S. Haldane
(1928).
• In 1936, a book “Origin of life” was published by A.I.
Oparin.
• Primitive atmosphere was reducing which consisting of chiefly methane (CH4), ammonia (NH3), water vapour, Hydrogen gas (H2), Nitrogen gas (N2).
• The atmosphere of earth at the time of origin of life was without free oxygen.
• Life is believed to be originated in water.
• An energy source such as solar radiation, lightening, and hot volcanic ash would have reacted with gases to form organic monomers.
• The first simplest organic compounds to be arise were hydrocarbons such as methane, ethylene, acetylene etc.
• Simple organic compounds accumulated in the ocean as a warm ‘dilute soup’.
• After formation of simple organic compounds, complex compounds like amino acids, fatty acids and sugars were formed by oxido-reduction reactions, condensation and polymerization reaction.
• According to Oparin, first living being was a protein
molecule, known as coacervates.
• Coacervates were certain complex inorganic and
organic compound in the hot sea water aggregated in different combinations.
• Sydney Fox Called them ‘microsphere’. These spheres have properties like metabolism, growth and budding.
• Amino acids, sugars, glycerol and fatty acids gave rise
to polymers, which may have assembled into spherical structures called protobionts.
• S.L. Miller and Harold C. Urey (1953) proved that amino
acids can be synthesized by the compounds present in the prehistoric atmosphere experimentally.
• In Miller and Urey’s experiment H2, H2O, CH4 and NH3 mixture is used.
• As a result of Miller and Urey’s experiment, red liquid
is formed by interaction of (above mixture) compounds. Few amino acids also detected in red liquid.
• The coacervates stared absorbing organic substances
of the ocean & become anaerobic chemoheterotrophs.
• The coacervates may have first evolved in the direction
of life on earth.
• The first organisms were virus like with simple
structure.
• The prokaryotes evolved before the eukaryotes. • The earliest prokaryotes must have been
chemoheterotrophs.
• The oldest fossil belong to blue-green algae. • The first organism to give off oxygen were probably
cyanobacteria.
• Organisms that can grow with or without oxygen gas
are called facultative anaerobes (or facultative aerobes).
• Organisms that are poisoned by oxygen gas are
obligate anaerobes e.g., Clostridium.
• Organisms that cannot grow without O2 gas are called obligate aerobes. e.g., all animals and plants.
• The oldest eukaryotic fossil is 1.5 billion years old. [ Organic Evolution : Organic Evolution can be
configured in two types (i) Divergent Evolution (ii) Convergent Evolution
(i) Divergent evolution (adaptive radiation) : –
Divergent Evolution is the development of different functional structures from a common ancestral form. Homologous organs support organic evolution (ii) Convergent evolution : Convergent Evolution is the development of similar adaptive functional structures in unrelated groups of organisms. Analogous organs disapprove organic evolution.
• The best evidence of organic evolution was given by (Von Baer father of developmental biology). According to Von Baer’s law (1825) :
(A) Generalized characters appears first. (B) Less generalized characters appears later. (C) Most specific characters appears last.
e.g., In birds, notochord appears first. Heart (4 chambered) appears later. Feathers appear lastly. • Bears’s law was modified by Haeckel. It was latter
called as biogenetic law.
• Biogenetic law states Ontogeny recapitulates Phylogeny i.e. Embryonic development repeats ancestral development.
• Geological time scale or stratographical scale is the calendar of earth’s past history indicating the evolution
of life through time recorded in the sequence of rocks. • Thus evolution is of two types (i) chemical evolution (ii)
organic evolution.
Table : Differences between features of chemical and organic evolution
S. No. Features Chemical evolution Organic evolution
1. Definition
It is the formation of the complex organic compounds from simple
compounds or elements.
It is the formation of complex form of life from simple form
of life.
2. Time of occurrence It occurred at the time of origin
and life. It is still occurring.
3. Reversibility Irreversible. Reversible.
DARWINISM OR THEORY OF NATURAL SELECTION
“Darwinism” or Theory of natural selection was
proposed jointly by Charles Darwin and Alffred Wallace in 1859. This theory was later on explained by Charles Darwin in his Book ”The origin of species” by means
of “Natural Selection” (1859)
( a ) Pos t ula t e s of D a rwinis m :
He had proposed six important postulates namely (i) Multiplication of individual of a species in a geometric proportion.
(ii) Existence of variation.
(iii) The operation of natural selection on the existing variability in order to select the best fitted variations. (iv) Due to geometric multiplication and due to the availability of limited food and space for these individuals the struggle for existence is seen. (v) Variations : They are rule of nature and proved to be beneficial for better existence.
(vi) Natural selection : Natural selection is the principle element of Darwin’s theory. The principle by which the
preservation of useful variations is brought about was called as natural selection.
( b) Merit s of D a rwinis m :
(i) The major achievement of Darwin was to recognize one of the major factor in adaptation
i.e. natural selection.
( c ) De me rit s of D a rwinis m :
(i)n Darwin’s natural selection principle the death of
the unit and the survival of the fittest was conceived. (ii) Darwin also believed that the natural selection operates on variations but he did not consider the possibility of the origin of new hereditary variations, which are really responsible for origin of species. (iii) Darwin also did not distinguish between hereditary and environmental variations.
( d ) Ne o– D a rwi nis m :
• It is a modified form of Darwinism, along with the recent
researches of Weisman, Mendel, Huxley, Gates, DeVries etc.
• They performed various experiments to remove
objections against Darwin’s Theory.
• Neo–Da rwin ism comp ris es t hree imp orta nt
postulates :
(i) Genetic variability : t means the variations that occur in the genetic constitution of an organism. They could be of following types :
(A) Chromosomal aberrations [deletion, duplication, translocation and inversion]
(B) Chromosomal numbers [ haploidy, polyploidy etc.] (C) Gene mutation
(D) Hybridization
(ii) Natural selection : According to Neo – Darwinism
the organism which is more adapted towards environment matures first and produces more progenies, as compaired to less adapted organism.
• t shows positive selection method.
• t can overcome environmental stress.
• t produces greater progeny than others.
(iii) Reproductive isolation : It is the failure of interbreeding between the related groups of living organisms and is essential to prevent the dilution of differences between the genetically different species.
LAMARCKISM
First theory of evolution was proposed by Jean Baptiste de Lamarck (1744–1829) in this book Philosophie
Zoologique (1809). The term Biology was given by Lamarck & Treviranus.
( a ) Ba s ic C onc e pt s of La ma rc kis m :
(i) Internal Vital Forces : Some internal forces are present in all organisms. By the presence of these forces organisms have the tendency to increase the size of organs or entire body.
(ii) Effect of environment and new needs : Environment influences all types of organisms. Changing environment gives rise to new needs. New needs or desires produce new structures and change habits of the organism.
(iii) Use and disuse of organs : If an organ is constantly used, it would be better developed whereas disuse of organ results in its degeneration.
(iv) nheritance of acquired characters : During the life time of an organism new characters develop due to internal vital forces, effect of environment, new needs and use and disuse of organs.
• These acquired characters are inherited from one
generation to another.
• By continuous inheritance through many generations
these acquired characters tend to make new generation quite different from its ancestors resulting in the formation of new species.
• Examples in support of Lamarckism :
(i) Long neck and large fore limbs of Giraffe.
(ii) Aquatic birds stretch their toes and developed webs. (iii) Snakes have lost their legs.
(iv) Deer become a good runner by the development of strong limbs and streamlined body.
(v) Retractile claws of carnivorous animals. ( b) C rit ic is m o f La ma rc k is m :
(i) According to first concept organisms tends to increase their size but it is not a universally truth, e.g. Among angiosperms the trees seem to have been primitive and the shrubs, herbs and grasses evolved from trees but the size is reduced during evolution. (ii) Second concept is false as we can’t have a sprout
wings wishing to fly like birds.
(iii) The third concept have some truth like the well developed biceps of black smith and less developed wings in flightless birds.
• But this concept also have many objections like the
eyes of regular reader do not increase in size and power with increasing age, the constantly beating heart maintains a constant size through generations. (iv) Forth concept is completely false because acquired characters are not inherited.
WEISMANN
Weismann cut off the tails of rats for about twenty two generations but there is no reduction in the size of the tail. On the basis of this experiment W eismann proposed the theory of continuity of germplasm. ( a) Acc ording t o We ismann :
• Two types of matters are present in organisms, somatoplasm and germplasm.
• Sometoplasm in somatic cells and germplasm in germinal cells.
• Somatoplasm dies with the death of an organism while germplasm is transferred into next generation. • f any variation develops in germplasm it is inherited while if variation develops in somatoplasm it is not transmitted.
NEOLAMARCKISM
Although Lamarckism remained controversial but some scientists gave following evidences in favour of Lamarckism they are called as neo lamarckians. According to neolamarckism environment affected the inheritance of acquired characters. According to it changing environment gives rise to some physical and chemical changes in organism which effect germplasm, and these acquired characters are definitely inherited.
MORPHOLOGICAL EVIDENCES OF EVOLUTION :
( a ) Homologous Orga ns or Homology :
[Same structure but different function] Homology can be defined as the relationship between the structures which have similarity due to common ancestors, although these structures may show difference in their functions. e.g.
(i) Fore limbs of vertebrates having pentadactyl limbs of similar origin and similar arrangement of bones, muscles etc.
(ii) Legs of different insects. (iii) Teeth of man.
Whale Birds Bat Horse Man ( b) Ana logous Org a ns or Ana logy :
[Different structure but similar function] Analogy can be defined as a relationship between structures, which though differ anatomically but would have superficial similarity due to similar functions. e.g.
(i) Wings of insects and wings of birds (ii) Sting of bee and scorpion.
(iii) Fins of fishes and flipper of whales.
( c ) Ve st igia l orga ns :
Those organs which have no longer function are known as vestigial organs. These organs have reduced structurally as well as functionally.
• t appears that these organs were well developed in ancestors but due to their reduced or less use they became functionless.
Fig : Vestigial organs of man
• There are many vestigial organs in human body. e.g.
(i) Vermiform appendix in man (ii) External ear in man. (iii) Nictitating membrane (iv) Wisdom tooth
• Common Ancestry and Inter-relationship : • Various organisms are interconnected.
• Their resemblance suggest a common ancestry
• e.g.
(i) Heart of fish is two chambered
(ii) Heart of amphibian is three chambered
(iii) Heart of birds and mammals is four chambered
EMBRYOLOGICAL EVIDENCES
• Embryology can be defined as a branch of science
that deals with study of development of an organism from zygote to an adult form inside the egg or mother’s
womb.
• The study of embryo’s from various organisms reveals
similarity in the early stages of embryo development and this theory suggests that these organisms have evolved from common ancestors.
• e.g. Embryos of fish, tortoise, child, rabbits and man show the similarity during embryo development.
PALENTOLOGICAL EVIDENCES
• Palaentology is a branch of science that deals with the
study of fossils.
• The study of fossils of some of the organisms show
similarity between the two groups,
• e.g. Fossils of Archaeopteryx shows characteristics of
both reptiles and birds.
CONNECTING LINKS
Animals are sharply differentiated and classified into phyla and classes but there are some existing animals which represent an intermediate position between the two groups. Such organisms are called as connecting links.
• e.g.
(i) Lung fish shows connection between fishes and amphibians.
(ii) Amphibians show connecting link between fishes and reptiles.
(iii) Virus show connecting links between living and non–living.
(iv) Euglena shows connecting link between plants and animals.
(v) Protospongia is a connecting link between protozoa and porifera.
SOME IMPORTANT POINTS RELATED WITH EVOLUTION
( a) Spe ciat ion :
(L. species - particular kind) it is the evolution of one or more new species from the pre-existing ones. An important requirement of speciation is the separation of the gene pool of the evolving population from other populations of the parent species so as to stop the gene flow.
•
Genetic Drift : It is random change in the allele number and allele frequency in a gene pool generally caused by small size of the population due to destruction of a major part of population or separation of a segment of from the rest. Chance leads to elimination of certain alleles and preponderance of others.Fig : Modes of speciation.
•
An Illustration to understand possible developmentof a species in various directions : A group of twelve
Beetles in the populations can generate variations because these are reproducing sexually. Crow can eat the beetles. The more beetles the crow eat, the
green
blue
Fig : An illustration to show evolution in different directions. • Case - I : Suddenly green beetle arises in red beetles
colony which can easily hide in plants, so crow can’t
see them & their population as compared to red beetles will increase by time.
• Case - II : Suddenly blue beetles arises in red beetle colony. Red beetles are killed by elephant foot but population of beetles grow slowly & blue bettle are more in number after sometime.
• Case - III : Because of poor nourishment average weight of beetles decreases. This change is not inherited over generations.
( b ) F os s ils :
The fossils can be defined as remains or impression of the hard parts of the past individual in the strata of the earth. The study of fossils is called palaeontology. (i) Fossilisation. (Formation of fossils) : The plants or animals are preserved and fossilized when they are buried in the lava of volcano, in the ice, in swamps, in an oil rich soil, in rocks, etc. Dead remain of aquatic animals and plants settle down at the bottom. Remains of terresterial organisms are also brought to sea and big lakes by rivers and streams. Mud and sand settle down continuously at the bottom. Sedimentation (deposition of layers) of mud and sand occurs. Fine mineral particles may penetrate the dead bodies.
Decay and disintegration of organic remains take place to leave only the harder parts, impressions, casts etc. The segmented mud and sand harden with time to form rocks.
(ii) Determination of the age of a fossil: There are two components to this estimation.
One is relative: If we dig into the earth and start finding fossils, it is reasonable to suppose that the fossils we find closer to the surface are more recent than the fossils we find in deeper layers.
• Radio-active dating : The age of a fossil can be calculated based on the property of a radio-active element uranium to transform into lead through several intermediate stages. Therefore, by calculating the amount of lead in a rock, one can approximately estimate the age of the rock and thus the age of the fossil present in it can be calculated.
• Fossils are formed and deposited in distinct layers one upon the other as described below
• About 100 million years ago, some invertebrates dies and got buried in the sand. More sand accumulated and sandstone was formed under pressure.
• Million years later, dinosaurs living in that area died and their bodies too buried in mud. This mud is compressed into rock. This layer is above the sandstone layer.
Fig : How do fossils form layer by layer • Again millions of years later, horse like creature died
and fossilized in rocks above previous mud rocks. • In later stages, water broke some of the rocks and
exposed the horse like fossils. Deeper we expose rocks older the fossils are observed.
HUMAN EVOLUTION
• The study of Human evolution and culture is known as Anthropology, which deals with fossil, prehistoric and living man.
• The sequential arrangement of stages in evolution is known as Geneology. • Man belogns to : Phylum -- Chordata Sub-phylum -- Vertebrata Class -- Mammalia Order -- Primates Sub order -- Anthropoidea Super family -- Hominoidea Family -- Hominidae
Genus -- Homo
Species -- Sapiens
[ Human ancestory : The arrangement of fossils in evolutionary sequence includes :
Tree shrews Prosimii early anthropoids
Dryopithecus Ramapithecus Australopithecus
Homo erectus Homo neanderthalensis
Cro-magnon Homo sapiens.
• Primates : Primates are found in the North American sediments from lower to upper Eocene time. Primates are placental mammals with nails, with clavicles, with orbits encircled by bone; possessing a brain. The primate order contains two sub orders : Prosimians
• Prosimians includes tree shrews, lemurs and tarsiers. • Tree shrews are certainly the most primitive of primates. Tree shrews are at present known only in the oriental region; where they are widely distributed. Lemurs are arboreal, primitive animals found both in Africa and Asia. Lemurs are generally nocturnal, hence, their eyes are large.
• Tarsiers are probably derived from lemouroid ancestors. It is an exclusively nocturnal, animal, its eyes are immense relative to the size of its head. • Anthropoids of all the primates, those which resemble
man most closely are the anthropoid apes.
The antropoids include new world Monkeys, old world monkeys and the hominoids.
[ Common Characteristics of Old World Monkey, Apes and Man :
(A) Reduced tail or absent.
(B) Erect posture with increase in the mentality. (C) Pinna comparatively smaller in size. (D) Increase in brain capacity.
(E) Decrease in number of lumbar vertebrae. (F) Menstrual cycle occurs in females.
The gibbon is the smallest of the anthropoid apes. The orangutan is a much larger ape often weighing over 100 ponds. The gorilla is much larger ape reaching weights in excess of 600 pounds. Apes (especially, the gorilla and chimpanzee) and man share common characteristics in the following :
(A) Lack of tail, large head, neck and large limbs. (B) Bipedal movement.
(C) Herbivorous, rarely carnivorous.
Evolution of man takes place in Pleistocene period. Dryopithecus was the common ancestor of humans and apes that lived an arboreal life in Asia as well as in Africa. The first Ramapithecus and Sivapithecus which lived in Africa and Asia (about 10 -15 million years ago) were the forerunners of homonids. These were first man like primates. The first fossil of Ramapithecus was a fragment of upper jaw from Shivalik hills of India. These has short face, small brain case, thickly enameled large teeth and walked on their knucles. (i) Australopithecus (The first man-ape) : These were intermediate between Ramapithecines and genus Homo. Its fossils were described by Raymond Dart in 1925 from South Africa. These were small statured forms averaging about 4 feet. These walked nearly or completely straight.
(ii) Homo habilis (Handy man) : Early Pleistocene man Nut cracker fossil man discovered by Leakey in 1960. They used chipped stone tools.
Their cranial capacity is 700 c.c.
(iii) Homo Erectus : Middle Pleistocene Man : Java and Peking man collectively named as Homo erectus by Mayer in 1950. Java man (Homo erectus = Pithecanthropus erectus) : Its fossils occurred in the Pleistocene. Its height was more than 5 feet. Peking man (Pithecanthropus pekinensis = Sinanthropus pekinensis). Probably lived like Java man. Peking man used fire. Used to live in caves in small groups. (iv) Late Pleistocene Man (Homo sapiens) : Homo sapiens were described as Homo neanderthalensis. The fossil primitive man were found in Europe, Asia
and Africa. These are Heidelberg man, Neanderthal man, Solo man and Rhodesian man.
(v) Heidelberg Man (Homo heidelbergensis) : It is known only from a massive lower jaw. The jaw is large and heavy and lacks a chin.
(vi) Neanderthal Man (Neanderthalensis) : These are considered to be on direct line of ancestory of modern man. Their fossils were found in the Neanderthal valley in Germany. These arose some 1,50,000 years ago and flourished in Europe, Asia and North Africa. The skull bones were thick, forehead was low and slanting. They use and construct flint tools.
(vii) Cro-magnon Man (Homo Sapiens Fossilis) : These lived during last 30, 000 years or more in Europe. Cro-magnons were about 180 cm in height with a large skull, broad face, rounded forehead, narrow nose, a prominent chin. They lack eyebrow ridges. These were cave dwelling and hunters. They made tools from finely chipped stones.They did not know agriculture and domestication but exhibited some cultural advances. (viii) Modern Man (Homo Sapiens Sapiens) : Developed after last glacial period i.e., about 10, 000 years ago. Homo sapiens sapiens appeared and began to spread all over the globe. Cranial capacity is about 1450-1600 cc. He learned to cultivate plants and domesticate animals of economic importance.These were the first settlers who started living a settled life. Modern man undergoes cultural evolution, primarily fabrication and use of tools.
(A) Palaeolithic age : Stone age, age of cave painting in latter period.
(B) Mesolithic age : Age of demestication of animals and learning, reading, writing, development of language.
(C) Neolithic age : Age of agriculture and knowledge.
NUTRITION
NUTRITION
“Nutrition” is a process of intake as well as utilization of nutrients by an organism. t also includes
breakdown of nutrients into smaller molecules and their absorption. Food provides us nutrition and energy.
t contains different types of nutrients in varying
amounts according to the need of our body.
• Nutrients : These are the substances required by
our body for its growth, repair, work and maintenance. Different types of nutrients are carbohydrates, fats, proteins, vitamins, minerals etc. Our daily energy need may vary according to our occupation, age, sex and under some specific conditions.
MODES OF NUTRITION
There are several modes of nutrition on the basis of which organisms are classified as follows :
Nutrition
Autotrophic They are able to synthesise their
own food.
Heterotrophic They are not able to synthesise their
own food.
(a ) Aut otrophic :
(Auto = self, trophic = food) It is a mode of nutrition in which organisms prepare their own food. Inorganic molecules like CO2 and H2O are converted into organic molecules like carbohydrates in the presence of sunlight and chlorophyll. e.g. Green plants. Autotrophs are further categorized as :
(i) Photoautotrophs : Those which utilize sunlight for preparing their food e.g. green plants.
(ii) Chemoautotrophs : Those which utilize chemical energy for preparing their food. e.g. Purple sulphur bacteria.
(b) Het e rot rophic :
(Hetero = different ; trophic = food) It is a mode of nutrition in which organisms derive their food from some other animals or plants. They cannot prepare their own food e.g. Human being, animals.
• On the Basis of Mode of Feeding Heterotrophs are Categorised as :
(i) Holozoic :It is a mode of nutrition in which
ingestion,digestion,absoption & assimilation takes place inside the body. e.g. Amoeba , Human etc. (ii) Saprotrophic : They absorb organic matter from dead and decaying organisms with the help of their
(iii) Parasitic : They derive/absorb their nutrition from other living plants or animals. e.g. Plasmodium, Round worm etc.
NUTRITION IN PLANTS
• Plants are photoautotrophic in nature. They prepare their
own food hence they are called as producers.
• They contain a green pigment called chlorophyll which
entrap solar energy which is then converted into chemical energy (ATP) which is utilized in preparation of food and the process is called as “Photosynthesis”. ( a ) P h o t o s y nt h e s i s :
(i) Definition : The synthesis of organic compounds
like glucose from simple inorganic molecules like CO2 & H2O by the cells of green plants having chlorophyll in the presence of sunlight is called as photosynthesis. (ii) Equation of photosynthesis :
6 CO2 + 12H2O Sunlight
Chlorophyll C6H12O6 + 6O2 + 6H2O (iii) Steps of photosynthesis : Photosynthesis is a two step process.
(A) Light reaction (B) Dark reaction ( b ) E s s e nt i a l s o f p ho t os y nt h e s i s :
(A) Sunlight :For plants sun is the basic source of
radiant energy.
• Plants utilize the light in the visible region of solar
spectra (electromagnetic spectrum) which comes under the range of 390 nm – 780 nm wavelength. • Visible region consists of white light which is a mixture
of 7 lights of different wavelengths.
• Maximum photosynthesis occurs in red region • There is minimum photosynthesis in green region
because green parts of plants reflect almost whole of the green light.
Visible IR
UV
V I B G Y O R
390 nm 780 nm
(B) Chlorophyll : These are the green pigments present in chloroplast. They are found in green leaves in the maximum amount as well as in other green aerial parts of plant. There are six different types of chlorophyll :chl a, b, c , d, e and bacteriochlorophyll. Amongst them chlorophyll a and chlorophyll b are the most commonly occurring chlorophyll.
• Besides chlorophyll certain other/ accessory
pigments are also present in plants like : (i) Carotenes : Orange in colour e.g. Carrot.
(ii) Xanthophylls : Orange yellow in colour e.g. Maize. (iii) Phycobilins : Different colours like red , violet
e.g. Blue-green algae, red algae etc.
( c ) Ra w Ma t e ri a ls of Phot os y nt he s is :
(A) Carbondioxide :Terrestrial plants obtain carbon
dioxide from the atmosphere through the small openings present on leaves called as stomata. ‘Stomata’ are the small pores present on the surface of leaves.
They help in exchange of gases and transpiration. Stomatal opening is guarded by the presence of guard cells (kidney shaped). Aquatic plants obtain CO2 dissolved in water through their general body surface so they perform more photosynthesis than terrestrial plants.
(B) Water : Plant’s roots absorb water from the soil by
the process of osmosis (endosmosis). This water is transported to leaves by a special type of tissue called as xylem.
• Plants utilize carbon dioxide during photosynthesis
and release it during respiration and both processes occur simultaneously. The intensity of light at which amount of CO2 used during photosynthesis becomes equal to the amount of CO2 released during respiration by plants is called as Compensation point.
• Compensation point occurs at low light intensity that
is during morning and during evening hours. ( d ) Sit e of P hot os y nt he s i s :
• Site of photosynthesis is different in prokaryotes and
eukaryotes.
• n prokaryotes : Photosynthesis occurs in lamellar
chromatophores.
• n eukaryotes : Photosynthesis occurs in chloroplast
• Chloroplast : Contain green pigment, called as chlorophyll.
• Chloroplast was discovered by Schimper.
• Number of chloroplasts is variable in different species
of plants.
• n lower plants like algae they are 1 or 2 in number.
• n higher plants their number varies from 40 – 100 or
more per palisade cell.
Internal structure of chloroplast
• Chloroplast also have variable shapes, for example
in algae cup shaped, ribbon shaped etc. While it is discoidal in higher plants.
• Chloroplast is a double membranous structure having
two parts :
(i) Grana :t is a lamellar system consisting of stacks
of granum lamella each is by a membranous box called as thylakoid. They are 40 – 60 per cell. Number
of thylakoids per grana is 50 or more. Chlorophyll molecules are found inside the thylakoid membrane where they trap solar energy in the form of small energy packets called ‘photons ‘or ‘ quanta’. Grana
are interconnected to each other by a channel called as stroma lamellae or Fret‘s channel.
(ii) Stroma :t is a non pigmented proteinaceous matrix
in which grana remain embedded. t contains enzymes
( e ) Me c h a n is m of Ph ot os y n t h e s is :
(i) Light reaction :
• It is also called as photochemical process.
• It was discovered by ‘Robert Hill’, therefore it is also
called as Hill’ s reaction.
• Site :Grana of chloroplast. • Requirements :Light and water.
• Regulated by :The process is regulated by chlorophyll
molecules.
• t consists of 3 steps :
(A) Photoexcitation of chlorophyll molecule :
During this process chlorophyll molecule receives sunlight in the form of small energy bundles called as photons and become excited to higher energy level.(B) Photolysis :It is also called as photooxidation of
water, this takes place in presence of Mn+2 and Cl–
ions.
4H2O 4H+ + O2 + 4e
–+ 2H
2O O2 is liberated as by product and H+ ions are used for reduction of NADP
2NADP + 4H+
2NADPH2
(C) Photophosphorylation :During this process ATP
are produced. It takes place in quantasomes / photosystem. Inorganic phosphate is required to convert ADP to ATP.
ADP + iP ATP
• Note : ATP and NADPH2 are called as assimilatory power.
(ii) Dark reaction :
• t is also called as thermo chemical reaction. • t was discovered by Melvin Calvin and Andy Benson
therefore it is also called as Calvin- Benson cycle. It’s
site is stroma of chloroplast.
• Raw materials :They require CO2 , NADPH2, ATP and Enzymes.
• Regulated by : Light reaction and enzymes.
• It involves three basic steps :
(A) Carboxylation : n this CO2 is captured by CO2 acceptors like RUBP (C3 Plants) PEP (C4Plants) with the help of carboxylase enzyme i.e. RuBisCO & PEPCo respectively. The first stable compound of C3 cycle is a three carbon containing molecule phosphoglyceric acid so it is called as C3 cycle while in C4 cycle it is four carbon containing oxalo acetic acid.
(B) Synthesis of glucose : n this phase captured
CO2 is assimilated into glucose in the presence of phosphatase and isomerase enzymes.
(C) Regeneration of RUBP.
• Note : Bacterial Photosynthesis - It is a special kind
of photosynthesis which takes place in certain bacteria. In this process also solar energy is utilised for the synthesis of carbohydrates and H2S is the hydrogen donor instead of water as in normal photosynthesis. So O2 is not liberated in bacterial photosynthesis.
NUTRITION IN ANIMALS
Animals are heterotrophic in nature . They are directly or indirectly dependent on plants to obtain their food • The mode of nutrition may be parasitic or saprotrophic
but usually animals are holozoic.
• All the basic steps of holozoic nutrition are same in unicellular to multicellular organism.
• Holozoic nutrition in animals consists of following 5-steps
(i)ngestion : The process of intake of food.
(ii) Digestion : It is the breakdown of large and complex molecules into simpler, smaller and soluble forms. (iii) Absorption : Taking up of the digested food through intestinal wall to blood or body fluid.
(iv) Assimilation : In this process absorbed food is taken by body cells.
(v) Egestion : The process by which undigested matter is expelled out.
(a) Nutrit ion in Amoeba :
• It is a unicellular organism living in water.
• Mode of nutrition is holozoic.
• The process of obtaining food is by phagocytosis (cell eating)
• Steps involved in nutrition in amoeba are :
(i) ngestion : Since it is unicellular so a single cell is
responsible for carrying out all the vital activities. Food is ingested with the help of pseudopodia. Animal engulfs the food particle lying near it by forming
(ii) Digestion : The enzymes from surrounding cytoplasm enter the food vacuole and break down the food into smaller & soluble forms. It is intracellular in Amoeba.
(iii) Absorption :The digested food is now absorbed
by cytoplasm by simple diffusion.
(iv) Assimilation : The food absorbed in amoeba is used to obtain energy from respiration, for its growth and reproduction.
(v) Egestion : Undigested food is thrown out of the cell.
Fig: Nutrition in amoeba
(b) Nutrition in Human Beings :
• Humans are holozoic and follow same 5- steps of
nutrition.
• Humans have highly evolved and complicated
digestive system consisting of an alimentary canal and different types of digestive glands.
• Alimentary canal :Long, hollow, tubular structure
consisting of various organs for digestion. Alimentary canal consists of following organs :
(i) Mouth : t is a small slit through which food is
ingested.
(ii) Buccal cavity : Mouth opens into a chamber called as buccal cavity. It has following components: 1. Hard palate: Roof of buccal cavity is called hard palate. 2. Tongue: At the floor of this cavity thick muscular structure is present called tongue. It helps in chewing, swallowing, tasting and speaking. Tongue has various types of taste papilla.
3. Teeth: Jaws present in buccal cavity are provided with four different types of teeth (Heterodont) :
ncisors : For cutting
Canines : For tearing
Premolars : For grinding
Molars : For grinding
• Dental formula of humans : In human beings two set of teeth appear during their life time
(Diphyodont)-(A) Milk teeth : These are temporary , arise at 6 – 11
month age, 20 in number
jaw lower Half jaw upper Half = 2 2 i , 1 1 c , 0 0 pm , 2 2 m (B) Permanent teeth : In adults
jaw lower Half jaw upper Half = 2 2 i , 1 1 c , 2 2 pm , 3 3 m
5. Three pairs of major salivary glands are found in mouth which release their secretions into the buccal cavity. They secret salivary amylase for starch digestion, so digestion of starch starts from here. • Note: Mouth continues in a funnel shaped pharynx. It
is the common passage between respiratory and digestive tract.
(iii) Oesophagus : Also called as food pipe . t leads
the food from mouth to stomach. Oesophagus has highly muscular walls, no digestion occurs here. (iv) Stomach :t is a ‘J’ shaped bag present on left
side of abdomen. It contains several branched and tubular glands present on the inner surface of its wall, which secret gastric juice.
(v) Small Intestine : t is a coiled and narrow tube
having 3 regions duodenum, jejunum , ileum. • On the inner wall of small intestine numerous finger
like projections are found which are called as villi, they increase the surface area of absorption.
• Duodenum is proximal part of small intestine,
receives secretion from liver and pancreas.
(vi) Large intestine : Small intestine opens into large intestine from where the undigested food material is passed to anus through rectum. It is divided into three parts : Caecum, Colon and Rectum.
