WJEC Biology Unit 2
BY2
Unit 2 Content:
• 2.1 All organisms are related through their evolutionary history
• 2.2 Adaptations for gas exchange
• 2.3 Transport
• 2.4 Reproductive strategies
• 2.5 Adaptations for nutrition
• 2.6 Adaptations for parasitism
2.1
All organisms are related through their evolutionary history
Biodiversity
What is biodiversity?
So it is a measure of the number of species
(and their variety) on the planet.
• The number of species (per unit area)
increases as you move from the poles towards the equator
• It peaks in the tropics
• Tropical rainforest and coral reefs are the most biodiverse habitats on the planet.
• Explore more about biodiversity here:
• Rainforest film here
(Attenborough Living Planet)
Evolution
Click on each icon to see two short video clips.
Produce a mind map of your ideas on evolution after watching the clips
Next
Homo sapiens
Humans vary enormously but we have all evolved from common ancestors.
What do you think humans will look like in the future?
cloc
What would happen in the next few years?
See next slide
cloc
Rat population
Follow the distribution of rat populations in Wales.
Number of rats
Time
Next
19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 20
Which graph most accurately represents the rat population growth? Take a vote
Next
Number of rats
Time
1
Example
Number of rats
Time
2
Number of rats
3
Example
Example
Number of rats
Time
1
Rat
Back
Number of rats
Time
2
Mouse
Back
Number of rats
Time
3
Lemming
Back
What do animals such as rats compete for?
Food Partner
Space
Variations in a population
Beautiful Ugly
Muscular Weak
Colourful
These rats show interesting variations within their population.
Why are there variations within a population?
Can you think of an advantageous variation in the rat population?
Next
Successful animals
Deer
Frog
Peacock
Cheetah Discuss why you think each animal seen
here is successful within its environment.
Survival
Why are fox populations increasing and polar bear populations decreasing?
Successful Less successful
What makes the cheetah better suited to its habitat than a gazelle?
Successful Less successful
Next
Why is Lance Armstrong so successful?
Survival Fittest
Date of birth: 1971
Winner of the tour de France: 7 times
Height: 1.77m
Weight: 75kg
He fought against leukemia and
survived . Click here for answer He has a larger heart than normal which beats stronger and slower than a normal person’s heart.
Click here for answer
Finches
Seeds Worms
Insects Fruits
The finches found on the Galapagos islands have a distinct beak shape variation.
Match the finch to its food and justify your choice. This is a drag and drop exercise.
Next
Charles Darwin
Year of birth:
1809
Place of birth:
Shrewsbury, England.
Voyage:
1832 to South America and the surrounding islands including the Galapagos.
Work:
Observed, described and classified plants and animals.
Click on the globe to get more information about the Galapagos Islands.
Natural selection
Discuss the adaptations shown by the finches studied by Darwin on the
Galapagos.
Use your discussions to agree on a definition for natural selection.
Compare your definition with one seen in a text book.
Next
Natural Selection Artificial Selection
Try and define artificial selection.
How does it vary from natural selection?
Numbers of the creature
Fur length
Fur Length
This graph represents the population growth of the little creature on the right!
It shows how fur length is related to population numbers.
This varies according to the
environment, as we will see on the next few slides
Next
Long hair
Using the pen tool, sketch an outline of population growth in this hot environment.
Numbers
Fur length
Short hair
Brrrrrrrrrrrrrrrr
Using the pen tool, sketch an outline of population growth in this cold environment.
Fur length
Next
Numbers of the creature
An environment where 6 months of the year is sunny
Z
Z Z
Z
Fur length
Using the pen tool, sketch an outline of population growth in this environment.
Numbers of the creature
An environment where 6 months of the year is cold
Z
Z Z
Z
Fur length
Using the pen tool, sketch an outline of population growth in this environment.
Next
Numbers of the creature
Stabilising selection tends to eliminate extreme variations from the population.
The middle phenotype tend to be selected for.
Frequency
Variation in phenotype
eliminated eliminated
retained
Before selection After selection
Variation in phenotype
Stabilising selection
Frequency
Variation in phenotype eliminated
retained
Before selection After selection
Variation in phenotype
Directional selection
Directional selection can happen when an environmental change occurs.
The change in the environment favours the organisms at one extreme of the phenotypes.
Next
Frequency
Variation in phenotype eliminated retained
Before selection After selection
Variation in phenotype
Disruptive selection
retained
two peaks
Disruptive selection is the opposite to be stabilising selection. Instead of favouring the mean, extremes of the population are selected. This is more uncommon and can be important in forming new species.
Number of individuals
Character
Graph A
Decide which type of selection the following graphs represent. Click on the appropriate box.
Next Stabilising
Directional Disruptive
Number of individuals
Character
Graph B
Decide which type of selection the following graphs represent. Click on the appropriate box.
Stabilising Directional Disruptive
Number of individuals
Character
Graph C
Decide which type of selection the following graphs represent. Click on the appropriate box.
Stabilising Directional Disruptive
Evolutionary History
The fossil record
shows most species are now extinct
Biodiversity has gone through Evolutionary bottlenecks
(mass extinctions)
Radiations of new species
Classification
• The classification of species is based on their evolutionary relationships
• One classification concept is that of the phylogenetic tree
Hierarchical system:
Kingdom Phylum Class
Order F amily Genus Species
Kinky People Can
Obtain
Frequent Great
Sex Animalia
Cordata
Mammalia Primates
Hominidae Homo
sapien
The 5 Kingdoms
Prokaryotae
Protoctista
Plantae Fungi
Animalia
Prokaryotae
Unicellular
Microscopic
No internal membrane based organelles
Protoctista
Eukaryotic
Many are single celled
No tissue differentiation
Plantae
Multicellular eukaryotes
Photosynthetic (autotrophic)
Cellulose cell wall
Fungi
Heterotrophic eukaryotes
Rigid cell wall (chitin)
Reproduce by spores
Animalia
Multicellular eukaryotic
Heterotrophic no cell wall
Nervous
coordination
Phyla
The animal kingdom is split into many different phyla
Each phylum has animals based on a shared basic
blueprint
Phylum: Annelids
Segmented worms
8000 species
earthworm, leech, lugworm
closed circulatory system
hydrostatic skeleton
specialised segments
thin permeable skin for gas exchange
Phylum: Arthropods
1 million named species!
Includes: Insects
crustaceans arachnids myriapods
All have: jointed legs
exoskeleton
fluid filled body cavity
• Insects are the most successful group of animals on earth
• Insects have 2 pairs of wings and six legs in the adult stage
Where are my wings then?
Phylum: Cordates
60,000 named species
• The vertebrates!
All possess a vertebral column or a backbone
• Well developed CNS and cranium
• Internal skeleton
• Subdivided:
Fish
• Scales
• Live in water
Amphibians
• Soft moist skin
• Simply lungs
• Live on land but water needed for
reproduction
Reptiles
• Dry scaly skin
• Lungs
• Land based
• Lay eggs with leathery shells
Birds
• Endothermic
• Lungs
• Feathers
• Forelimbs adapted for flight
• Eggs with hard shells
Mammals
• Endothermic
• Lungs
• Hair
• Double circulation
• Internal gestation and mammary glands
• Sweat glands
Identifying Species
• Morphological definition of a species
• Similar morphology can be used to identify closely related species
e.g. pentadactyl limb in vertebrates
• Analogous structures cant be used – wings?
Biochemical methods
• The proportion of genes or proteins shared
between species can be used to estimate
relatedness
• Gel electrophoresis is used
• Reduces mistakes made by convergent evolution
