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Chapter 5
Chapter 5
Biological Concepts
Key Concepts
• To understand living organisms, one must
have a basic understanding of the variety
of compounds from which organisms are
built.
• Four groups of macromolecules are
necessary for life: carbohydrates, lipids,
proteins, and nucleic acids.
Key Concepts
• Cells can be either prokaryotic or eukaryotic • Cells produce new cells by the process of cell
division
• Evolution is the process by which the genetic
composition of populations of organisms changes over time
• Natural selection favors the survival and
reproduction of those organisms that possess
Key Concepts
• A species is a group of physically similar,
potentially interbreeding organisms that
share a gene pool, are reproductively
isolated from other such groups, and are
able to produce viable offspring.
• The binomial system of nomenclature
uses two words, the genus and the
Key Concepts
• Most biologists classify organisms into one
of three domains, categories that reflect
theories about evolutionary relationships.
• Phylogenetic trees and cladograms
Building Blocks of Life
• Macromolecules (large molecules) are some
of the most important chemical compounds
in organisms
• 4 major classes of macromolecules in living
organisms are:
– carbohydrates – lipids
– proteins
Carbohydrates
• Contain C, H and O, frequently in a 1:2:1
ratio, – CH
2O, thus the name
carbohydrate (carbon water)
• Sugars and polysaccharides are the two
most common carbohydrates in living
Carbohydrates
• Sugars
– monosaccharides are simple sugars, usually with 5 or 6 C atoms
• ribose and deoxyribes are in nucleic acids • glucose is the basic fuel molecule for cells
– disaccharides consist of 2 monosaccharides bonded together
– types of disaccharides
• sucrose = glucose + fructose (table sugar) • maltose = glucose + glucose
Carbohydrates
• Polysaccharides
– these carbohydrates are polymers, large
molecules consisting of the same basic units linked together
– storage forms of polysaccharides
• starches in plants, algae, and some microorganisms, made of units of glucose
• glycogen, “animal starch” is produced by animals and some microorganisms to store glucose for future use
– structural polysaccharides
• cellulose is found in cell walls of plants, algae
Lipids
• Fats, Oils & Waxes
• Composed primarily of C and H
– fatty acids: long hydrocarbon chains containing an acid group
– Triglycerides: simple fats composed of 3 fatty acids attached to a glycerol molecule
• Functions within marine organisms
– store energy, cushion organs, buoyancy – phospholipids are part of cell membranes
– steroids, which have complex ring structures, are chemical messengers, e.g., testosterone
Proteins
• Proteins are polymers of amino acids
– 20 different amino acids make up proteins
– polypeptides—chains of amino acids, which are coiled and folded into complex, three-dimensional protein molecules
• Functions of proteins
– compose primary structural components of animals: muscles and connective tissue
Nucleic Acids
• Nucleic acids—polymers of nucleotides
– Nucleotides are composed of 5-carbon sugar + nitrogen-containing base + phosphate group
• DNA & RNA
Nucleic Acids
• DNA (deoxyribonucleic acid)
– Large, double stranded, helix-shaped molecule
• sugar = deoxyribose
• N-containing base = adenine, guanine, cytosine or thymine
– DNA
• contains genes (genetic material) • genes direct synthesis of proteins
5’
3
’
5’
3
Nucleic Acids
• RNA (ribonucleic acid)
– usually a single-stranded molecule
• sugar = ribose
• N-containing base = adenine, guanine, cytosine or uracil
– functions in protein synthesis
Cells
• Cells are basic units of living organisms
• All cells are capable of basic processes:
– metabolism – growth
– reproduction
• Surrounded by cell membrane
Types of Cells
• Prokaryotic cells (e.g. bacteria, archaeans)
– lack a nucleus and membrane-bound organelles
– prokaryotes (prokaryotic organisms) are always unicellular
• Eukaryotic cells (e.g. plants, animals)
– have a well-defined nucleus and many membrane-bound organelles
Organelles
• Have specific functions within cell
• Nucleus and ribosomes
– Nucleus: large structure surrounded by a
nuclear membrane which contains the cell’s DNA and acts as the control center
• Chromosomes, which contain an organism’s genes, is composed of DNA + protein
– ribosomes, which function in the synthesis of proteins, are assembled in an area of the
Organelles
• Organelles involved in synthesis,
processing, and storage
– endoplasmic reticulum (ER): series of
membranes winding through cytoplasm in eukaryotic cells
• rough ER has ribosomes attached to its surface, and functions in modification of proteins during synthesis • smooth ER (no ribosomes) functions in synthesis of
Organelles
– Golgi apparatus—functions in the modification of proteins and places membranes around
them
– lysosomes—membrane-bound sacs produced by the Golgi apparatus which contain
enzymes that function in digestion
– vacuoles—structures surrounded by a
Organelles
• Organelles involved in energy conversion
– reproduce themselves
– chloroplasts—organelles found in photosynthetic organisms that convert radiant energy of light
into chemical energy
– mitochondria—organelles which transfer chemical energy in food into molecules of adenosine triphosphate (ATP)
Organelles
• Organelles of movement
– Flagella: long, hair-like organelles (usually 1 to 4 per cell) used to propel the cell through the watery environment
– Cilia: short, hair-like organelles which are
PHOTOSYNTHESIS CELLULAR RESPIRATION Algae and phytoplankton (autotrophs) Sun
Seagrass and seaweed (autotrophs) Glucose (energy-rich) Animal (heterotroph) O2
CO2 + H2O (energy-poor)
Stepped Art
Energy Transfer in Cells
• Photosynthesis
– low-energy molecules (CO2 and H2O) combine to form high-energy food molecules
(carbohydrates)
– in eukaryotes, photosynthesis occurs within chloroplasts
– chloroplasts
• two membranes
• thylakoids, arranged in stacks (grana)
Energy Transfer in Cells
• Cellular respiration
– releases energy from food molecules – most occurs within mitochondria
• two membranes, with inner membrane folded many times to form mitochondrial cristae
Cellular Reproduction
• Cell division in prokaryotes
– have a single, circular chromosome
Cellular Reproduction
• Cell division in eukaryotes
– mitosis—(occurs after duplication of all chromosomes) nuclear membrane
disappears, chromosomes separate, and new membranes form to make 2 copies
– after mitosis, the cell divides (cytokinesis)
(b) Eukaryote Chromosome is duplicated Cell splits into two (a) Prokaryote Chromosome Chromosomes separating Stepped Art
Levels of Organization
• Cells within a multicellular organism that
serve 1 particular function are grouped
into tissues
• Several different tissues can combine into
structures called organs
a) cell
Smallest unit that can live and reproduce on its own or as part of a multicelled organism. It has an outer
membrane, DNA, and other components.
b) tissue
Structural unit of certain types and proportions of cells interacting in some task. Many cells (white) made this bone tissue from their own secretions.
c) organ
Structural unit of two or more tissues interacting in some task. A parrotfish eye is a sensory organ used in vision.
d) organ system
Organs interacting physically, chemically, or both in some task. Parrotfish skin is an integumentary system with tissue layers, organs such as glands, and other parts.
e) multicelled organism
Individual made of different types of cells. Cells of most
organisms, including this Red Sea parrotfish, are organized as
tissues, organs, and organ systems.
Stepped Art
Evolution and Natural Selection
• Evolution—the process by which
populations of organisms change over
time
• Evolutionary biology investigates:
– how and when organisms evolved – what role the environment plays in
Darwin and the Theory for Evolution
• Voyage of discovery
– Darwin traveled on the HMS Beagle for 5 years, beginning in 1831
– Darwin was influenced by Charles Lyell and other geologists who concluded that:
• since geological change is slow and continuous, the earth is very old
Darwin and the Theory for Evolution
• Formulating a theory for evolution
– Darwin was inspired by Thomas Malthus’s essay about factors that control the human population
– Darwin developed his hypothesis “evolution by natural selection” to explain why populations generally do not exhibit unchecked growth and how they change over time
Darwin and the Theory for Evolution
• Theory of evolution by natural selection
– artificial selection is practiced by farmers and breeders to obtain desirable traits in
plants/animals
– Darwin believed a similar process was occurring in nature
– natural selection favors survival and
Darwin and the Theory for Evolution
– Four basic premises of Darwin’s theory
1. All organisms produce more offspring than can possibly survive to reproduce.
2. There is a great deal of variation in traits among individuals in natural populations. Many of these variations can be inherited.
3. The amount of resources (e.g., food, light, living space) necessary for survival is limited.
Darwin and the Theory for Evolution
4. Those organisms that inherit traits that make them better adapted to their environment are
more successful in the competition for resources. They are more likely to survive and produce
more offspring. The offspring inherit their parents’ traits, and they continue to reproduce, increasing the number of individuals in a population with the adaptations necessary for survival.
– an organism evolves traits that are
Genes and Natural Selection
• When Darwin proposed theory of evolution
by natural selection, cell division, genes and
chromosomes had not been discovered.
• Modern evolutionary theory
– the modern synthetic theory of evolution is
essentially Darwin’s 1858 idea refined by modern genetics
– genes
• produce traits when genetic information is translated into proteins
• can exist in different forms called alleles
a) A pair of homologous chromosomes, each in the unduplicated state (most often, one from a male parent and its partner from a female parent)
b) A pair of alleles (each being a certain molecular form of a gene) on a pair of homologous chromosomes
c) Three pairs of genes; regions of DNA that code for specific proteins
Stepped Art
Genes and Natural Selection
• Role of reproduction
– in asexual
reproduction, offspring are clones of and
identical the single parent, variation
Genes and Natural Selection
• Role of reproduction
– in sexual reproduction, chromosomes from 2 parents are combined
• gametes (sex cells) unite during fertilization • gametes have a haploid number (N) of
chromosomes instead of a diploid number (2N) • the haploid number of chromosomes from 2
egg ASEXUAL REPRODUCTION
SEXUAL REPRODUCTION Sperm
Fertilized egg
Stepped Art
Genes and Natural Selection
• Role of reproduction (con’t)
– meiosis (reduction division) is special kind of cell division that forms haploid cells called gametes
• chromosomes are duplicated once, and the cell divides twice
• results in cells with ½ the number of chromosomes in the parent cell
• during the initial phase, chromosomes connect and allow crossing over and recombination
Stepped Art
Genes and Natural Selection
• Population genetics
– organisms must adapt to changing environmental conditions in order to survive
– ability to adapt is limited by the gene pool
– Only individuals that have combinations of genes and alleles that allow adaptations to their
surroundings are likely to survive and reproduce – fitness (biological success) is measured by the
Evolution of New Species
• Typological definition of species
– based on morphology, the structure and appearance of the organism
– a species defined this way will have a definable set of characteristics different from those of other species
– Type Specimen = museum specimen considered to be representative of the species
– weaknesses of typological definition
• males may look different than females (sexual dimorphism) and juveniles than adults
• Modern species definition
– a species is one or more populations of
potentially interbreeding organisms that are reproductively isolated from other such
groups
– reproductive isolation: members of a different species are not in the same place at the same time or are physically incapable of breeding, so genes from different species are not mixed
• Modern species definition (con’t)
– isolating mechanisms that prevent fertilization
• habitat isolation—similar species of organisms live apart and never encounter each other
• anatomical isolation—incompatible copulatory organs prevent similar species from reproducing with one
another
• behavioral isolation—exhibiting of special behaviors during the breeding season, so that only members of the same species recognize the behavior as courtship • temporal isolation—the time members of one species
are ready to reproduce does not coincide with the time members of a related species reproduce
• biochemical isolation—biochemical or genetic differences between the gametes of 2 species prevent successful copulation from resulting in offspring
– isolating mechanisms that prevent successful reproduction following fertilization
• incompatible genes or biochemical differences can prevent a fertilized egg from developing further
• the hybrid offspring may survive but be infertile or poorly equipped to compete, dies out without
reproducing
• Speciation: refers to mechanism by which
new species arise
• Process of speciation
– allopatric speciation: 2 or more populations of the same species become geographically
isolated
– gene flow between the 2 populations stops
– natural selection operates on each segment of the original population independently
Classification: Bringing Order to Diversity
• Linneaus and the binomial system of
naming
– binomial nomenclature: system of naming that uses 2 words, the genus and species epithet – introduced by Swedish botanist Karl von
Linné (Carolus Linnaeus) in 1750
– e.g. Chaetodon longirostris (long-nose
• Taxonomic categories
– Early schemes of classification
• all living things were classified into 1 of 2 kingdoms, Animalia and Plantae, until 1960s
– Modern classification
• major categories: domain, kingdom, phylum, class, order, family, genus, and species
• domains: Archaea, Eubacteria, Eukarya
• kingdoms: Eukarya contains 3 kingdoms, Fungi, Plantae and Animalia
• protists: eukaryotic organisms that do not fit the definition of animal, plant or fungus
• Phylogeny: evolutionary history of a
species or group of related species
– phylogenetic tree: traditional representation of phylogeny
– phenetics: classification of organisms based on similar characteristics with little attention to when these characteristics evolved.
– cladistics: bases classification on the order in time that the branches arise along a
phylogenetic tree called a cladogram, ignores similarity of structure
