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

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Homo sapiens

Humans vary enormously but we have all evolved from common ancestors.

What do you think humans will look like in the future?

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cloc

What would happen in the next few years? See next slide

cloc

Rat population

Follow the distribution of rat populations in Wales.

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Which graph most accurately represents the rat population growth? Take a vote

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Example

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Example

Example

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Rat

Back

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Mouse

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Lemming

Back

What do animals such as rats compete for?

Food Partner

Space

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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?

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Successful animals

Deer

Frog

Peacock

Cheetah

Discuss why you think each animal seen here is successful within its environment.

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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

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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

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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.

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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.

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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.

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Natural Selection Artificial Selection

Try and define artificial selection. How does it vary from natural selection?

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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

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Long hair

Using the pen tool, sketch an outline of population growth in this hot environment.

Numbers

Fur length

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Short hair

Brrrrrrrrrrrrrrrr

Using the pen tool, sketch an outline of population growth in this cold environment.

Fur length

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Numbers of the creature

An environment where 6 months of the year is sunny

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Fur length

Using the pen tool, sketch an outline of population growth in this environment.

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Numbers of the creature

An environment where 6 months of the year is cold

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Fur length

Using the pen tool, sketch an outline of population growth in this environment.

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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

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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.

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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.

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Number of individuals

Character

Graph A

Decide which type of selection the following graphs represent. Click on the appropriate box.

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Stabilising

Directional

Disruptive

Number of individuals

Character

Graph B

Decide which type of selection the following graphs represent. Click on the appropriate box.

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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

Family

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