Evolution

WJEC Biology Module 1

Learning outcomes

• know that heritable variation is the basis of evolution.

Adaptation and Evolution

• Organisms are well adapted to their particular environment

• Variation occurs due to the inheritance of different alleles

• These two ideas are closely related and help explain evolution

Pupil Activity• BBC video – the life of mammals

– Watch episode one – a winning design What features make mammals better adapted to

survive? What evidence for evolution is discussed in this film? Account for the differences between the types of

mammals found– Monotremes – Australia– Marsupials – Australia and South America– Placentals – the rest of the world

Learning Outcomes

• Consider how individuals with characteristics adapted to their environment are more likely to survive and breed successfully.

• Discuss the use and limitations of a model to illustrate the effect of camouflage colouring in predator and prey relationships.

Camouflage Colouring

• Polar environments are covered with snow– It is a selective advantage for the

organisms to be white• Prey

– Are camouflaged and will avoid being eaten

• Predator– Can approach prey without being noticed

Adapting to Polar Environments

• Variation within a population will give different shades

• Paler shades have a survival advantage• Paler individuals survive to breed• Pass on “pale” genes to their offspring• More pale individuals in the next

generation• Over time the population changes

making them better adapted to the environment.

Pupil Activity

• Think of an animal which is camouflaged in it’s habitat.

• Explain in terms of evolution how that colouration came about.

Pupil Activity• Modelling Natural Selection using predation

and camouflage

• In the natural environment you must consider– Size of population– Immigration or emigration– Random mutation– Do variations influence survival in other ways

• In the lab we can design experiments to demonstrate this!!

Learning Outcomes

• know that the genes which have enabled these better adapted individuals to survive are then passed on to the next generation. – This is natural selection as proposed by

Charles Darwin and accepted by scientists. Work continues to fully understand the process as further evidence from genetics and molecular biology is collected. The process of natural selection is sometimes too slow for organisms to adapt to new environmental conditions and so organisms may become extinct.

Evolution• Charles Darwin developed the theory of

natural selection as a driving force of evolution

• Two facts– Organisms have a tendency to overproduce,

meaning offspring are more numerous than their parents

– Populations remain relatively stable

• Deductions– “struggle for existence” – competition – Better adapted survive to reproduce– favourable adaptations inherited

The theory of natural selection• Variation• Overproduction• Competition for resources - Struggle for

existence• Best adapted organisms survive –

“Survival of the fittest”• Advantageous features inherited• Gradual change in the population

Darwin’s Finches

• Darwin noticed that there were species of finch were only found on certain islands in the Galapagos Archipelago

• Each species had their own specific characteristics– Beak shape and size seemed to reflect the food they ate

Darwin’s Ponderings

• Why should the species which are supposed to have been created in the Galapagos Archipelago, and nowhere else, bear so plain a stamp of affinity to those created in America?

Darwin’s Finches

• There were two hypotheses• Hypothesis 1

– God created all finches separately• Science can not prove or disprove the

actions of a god, as the laws of science are not obeyed

• Any hypothesis involving the actions of a god can not be a “scientific hypothesis”

• Hypothesis 2– The characteristics has been acquired

and then inherited

So which Hypothesis

• Darwin’s observations did not support these hypotheses.

• Darwin developed his Theory of Natural Selection to explain the evidence– Overproduction– Variation– Better adapted survive– Breed and pass on genes– Characteristic inherited and the species

gradually change

Theory or Hypothesis or Law

• Theory– An idea that seeks to explain a scientific

phenomena– Generally accepted– Supported by evidence

• Hypothesis– A suggested explanation for an event or

observation– A statement which can be tested by

experimentation• Law

– Describes how something works and can be used to predict things

Extinction

• Species may become extinct due to a variety of reasons– It has failed to adapt successfully to its

environment– Another species is better adapted and it

is out competed– Sudden change in environment and the

species can not survive in the new conditions

Peppered Moth

• Peppered moths rest on silver birch tree trunks with their wings outstretched, this behaviour can make them easy prey for birds. Originally the peppered moth was only recorded in the paler speckled form, but during the industrial revolution in the UK (about 200 years ago) dark coloured peppered moths started to be recorded.

• Whilst the numbers of the dark form of the peppered moth increased dramatically, the paler speckled form became scarce in some areas. However, in more recent times the numbers of the dark form have declined relative to the pale form.

Pale coloured, speckled peppered moth

Peppered moth“A modern example of evolution”

Dark coloured peppered moth

Peppered moth“A modern example of evolution”

Peppered moth“A modern example of evolution”

Peppered moths on tree trunk

Peppered MothJan 08 (H) Question 8

Selection in action - banded snails

•  The purpose of this activity is:– to interpret data about changing

populations using ideas about natural selection

– to make predictions about how populations might change in the future

Banded Snails - Answers

1. This could be because the yellow snails are better camouflaged in June– Give a suggested reason why

2. The woodland results show that the snails are more commonly not yellow, and, usually have one or no bands.

3. In hedgerows and grassland, around 65 % of the snails (±35%) are yellow, and 35% (±30 %) have one or no band – so most have more than one band.

4. Yellow snails are more common in hedgerows and grassland. If the amount of woodland decreased, it is possible that the numbers of yellow snails would increase.

Natural Selection In GuppiesWJEC Exam Question June 08 (Higher)

• (a)– 1. Variation in colour/pattern– 2. results from mutation/change in genes/DNA– 3. Natural selection by predation/survival of the

fittest– 4. and sexual selection/females select most

colourful males to breed– 5. Most colourful males survive/are at an

advantage– 6. to pass on genes

• (b) – (i) Evolution – (ii) (Charles) Darwin

Natural Selection – GuppiesA perfect Answer

• Variation in colour• results from mutation• Natural selection by predation and females

select most colourful males to breed• Most colourful males survive• to pass on genes

Learning outcomes

• understand that evolution is ongoing as shown by the development of resistance to antimicrobial chemicals by bacteria or Warfarin resistance in rats

Natural Selection in Action

Antibiotic resistance in bacteria

Super-rats in Wales

Antibiotic resistance in Bacteria

• Antibiotics are chemicals designed to kill bacteria

• Mutations in genes have led to the development of anti-biotic resistance in some strains of bacteria– Mutated bacteria has a selective advantage– reproduces– Mutated gene passed on to next generation– Population of bacteria becomes resistant to

anti- biotics

• Penicillin resistance – bacteria produce an enzyme that can break down penicillin

• New problems – Resistant strains of tuberculosis bacteria– MRSA (methicillin resistant staphylococcus

aureus)

Super-rats in Wales• Warfarin is a popular rat poison

– Prevents blood clotting– Capillaries burst– Rat bleeds to death

• Some rats have developed Warfarin resistance– Blood clotting is not affected by warfarin

WJEC Exam Question 7 - Jan 07• (a) Rats / rodents / mice• (b)

– (i) mutation– (ii) genes / DNA / Alleles

• (c)– Adaptation / mutation– Helped survival / an advantage– Passed on– Through genes– Natural selection / survival of the fittest (to breed)– Lead to evolution of a new type

• (d)– Shows a change in a species– Taking place in/over very short time– Illustrates natural selection / survival of the fittest

Fossil evidence• Fossils are “remains” of plants and

animals from many years ago which are found in rocks. Fossils can be formed from:– Hard parts of animals which do not decay

easily– Preservation – where one of the factors

necessary for decay is absent e.g. mummification

– Petrification - minerals replace parts of plants and animals as they decay.

– Casts – the decaying matter leaves an imprint behind in the rock

Practice QuestionsBird Skeleton Jan 09

• (a) – Fossils [1]

• (b) – Makes (skeleton) light weight (for flying)

[1]– (not: helps them to fly/ref. insulation)

• (c) – Shows features of birds and

reptiles/description e.g. has teeth and wings [1]

– Reptile remains pre-date bird remains / Reptile remains found in rocks older than rocks in which birds remains are found / or ref to actual numbers of years [1]

• (d) – Air spaces an advantage [1]– Genes passed on (to future generations)

[1]– reference to mutation occurring [1]

Practice QuestionsMoa and Ostrich

Practice QuestionsHumans – milk digestion