WJEC Biology Unit 2
BY2
Unit 2 Content:
• 2.1
•
•
•
•
•
2.2
2.3
2.4
2.5
2.6
All organisms are related through
their evolutionary history
Adaptations for gas exchange
Transport
Reproductive strategies
Adaptations for nutrition
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
Produce a mind map of your ideas on
evolution after watching the clips
Click on each icon
to see two short video 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?
Next
Follow the distribution of rat populations in
Wales.
Number of rats
cloc
Time
Rat population
What would happen in the next
few years?
Next
See next slide
Which graph most accurately represents the
rat population growth? Take a vote
Number of rats
1
20
19
18
17
16
Time
15
Example
2
14
13
Number of rats
12
11
10
9
8
7
6
5
Time
Example
3
4
3
Number of rats
2
1
Next
Time
Example
Number of rats
1
Rat
Time
Back
Number of rats
2
Mouse
Time
Back
Number of rats
3
Lemming
Time
Back
What do animals such as rats compete for?
Food
Partner
Space
Next
Variations in a population
These rats show interesting variations within their population.
Beautiful
Ugly
Weak
Why are there variations within a population?
Can you think of an advantageous variation in the
rat population?
Colourful
Muscular
Next
Successful animals
Frog
Deer
Discuss why you think each animal seen
here is successful within its environment.
Cheetah
Peacock
Next
Survival
Successful
Less successful
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?
Next
Why is Lance Armstrong so successful?
Date of birth: 1971
Winner of the tour de France: 7
times
Height: 1.77m
Weight: 75kg
Survival
He fought against leukemia and
Click here for answer
survived .
Fittest
He has a larger heart than normal
Clickstronger
here forand
answer
which beats
slower
than a normal person’s heart.
Next
Finches
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.
Fruits
Worms
Insects
Seeds
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.
Next
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?
Next
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
Numbers of
the creature
Fur length
Next
Long hair
Using the pen tool, sketch an
outline of population growth in
this hot environment.
Numbers
Fur length
Next
Short hair
Using the pen tool, sketch an
outline of population growth in
this cold environment.
Brrrrrrrrrrrrrrrr
Numbers of
the creature
Fur length
Next
An environment where 6 months of
the year is sunny
Using the pen tool, sketch an
outline of population growth in
this environment.
Z
Z
Z
Numbers of
the creature
Z
Fur length
Next
An environment where 6 months of
the year is cold
Using the pen tool, sketch an
outline of population growth in
this environment.
Z
Z
Z
Numbers of
the creature
Z
Fur length
Next
Stabilising selection tends to eliminate extreme variations from the population.
The middle phenotype tend to be selected for.
Stabilising selection
Before selection
After selection
eliminated
eliminated
retained
Frequency
Variation in phenotype
Variation in phenotype
Next
Directional selection can happen when an environmental change occurs.
The change in the environment favours the organisms at one extreme of
the phenotypes.
Directional selection
Before selection
After selection
eliminated
retained
Frequency
Variation in phenotype
Variation in phenotype
Next
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.
Disruptive selection
Before selection
After selection
retained
retained
eliminated
two peaks
Variation in phenotype
Variation in phenotype
Frequency
Next
Decide which type of selection the following graphs
represent. Click on the appropriate box.
Stabilising
Directional
Disruptive
Graph A
Number of
individuals
Character
Next
Decide which type of selection the following graphs
represent. Click on the appropriate box.
Stabilising
Directional
Disruptive
Graph B
Number of
individuals
Character
Next
Decide which type of selection the following graphs
represent. Click on the appropriate box.
Stabilising
Directional
Disruptive
Graph C
Number of
individuals
Character
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
Family
Genus
Species
Animalia
Cordata
Mammalia
Primates
Hominidae
Homo
sapien
Kinky
People
Can
Obtain
Frequent
Great
Sex
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