AS Biology UNIT F212 Module 3 – Biodiversity and Evolution Evolution Sona Arya E – mail: sona.arya@stokesfc.ac.uk

Aims To provide an overview of Evolution All tasks/activities are on the worksheet given last lesson – also on Moodle under “Revision Activities” OCR Biology 1 Chapter on Moodle on Evolution

Exam Objective Define the term variation The presence of differences between individuals

Variation between individuals may be due to…… Mutations in the genes or chromosomes. Meiosis, which produces non- identical gametes. Random fertilisation of the eggs.

Random fertilisation

So each gamete produced by an individual is unique and can lead to variation

Exam Objectives Discuss the fact that variation occurs within a species as well as between species

Which is Which? Intraspecific or Interspecific? Within species? E.g. Weight, colour of beak of same birds Between species? Interspecific E.g. Weight, colour of beak of different types of birds

Continuous and Discontinuous Variation in which there is a full range of intermediate values between two extremes Continuous Variation in which there are discrete groups with no intermediate values Discontinuous

Discontinuous variation

Exam Objectives Describe the differences between continuous and discontinuous variation using examples found in a range of characteristics found in plants animals microorganisms

On your white boards .... Continuous or Discontinuous? Sex Discontinuous Antibiotic resistance Length of leaves of plants Continuous Colour

On your white boards .... Continuous or Discontinuous? Blood Group Discontinuous Presence of flagella Number of leaves Continuous Height

Variation Differences between individuals can be produced by Genetic and /or Environmental influences What does this mean?

Exam Objectives Explain both genetic and environmental causes of variation

Genetic Variation Involves different versions of the same genes (alleles) Genes and alleles make up an organisms genotype and phenotype (displayed characteristics) Inherit genes from parents Variation is inherited E.g: Blood group (humans) Antibiotic Resistance in bacteria

Environmental Variation Involves differences in the environment e.g. Climate, diet, lifestyle Characteristics can change over an organism’s life E.g: accents Pierced ears

Both Genetic factors determine what characteristics an organism is born with, but environmental factors can influence how some characteristics develop E.g. Height Flagellum

Adaptations Behavioural Adaptations

Physiological Adaptations

Anatomical Adaptations

Examples of the adaptations of xerophytes

Exam Objectives Outline the behavioural, physiological and anatomical (structural) adaptations of organisms to their environment Do as Table using Revision Guide / Textbook

Examples of adaptations which help organisms survive p3 Behavioural Earthworm burrows when touched to avoid predators and drying out Hedgehog rolls into a ball to avoid predators Fennec fox in desert remains in burrow in day and emerges at night Venus flytrap plant leaves close around insect when sensitive hairs touched Stomata of xerophyte may open at night and close in day Physiological Humans produce more haemoglobin at high altitudes Humans with sickle cell allele can survive malaria Plants near the sea have cytoplasm with low water potential so water is still absorbed by osmosis Venus flytrap plant leaves secrete extracellular enzymes which digest insects Yeast fungus can respire aerobically or anaerobically Some bacteria species have alleles for antibiotic resistance Anatomical Mammals e.g. cats have hair for heat insulation Mammal predators e.g. lions have large canine teeth to kill Fennec fox in desert has large ears to lose heat effectively and give good direction of sound Xerophytic plants have long roots, thick waxy cuticle, leaves with small surface area, rolled leaves, stem stores water, fewer stomata, protected stomata Bacteria may have a flagellum for locomotion

Exam Question Hedgehogs are commonly found in gardens throughout the UK. They are brown with small ears, feet with claws and long, spiky fur. They hibernate over winter and can roll into a ball when alarmed. Question Describe one behavioural, one physiological and two anatomical adaptations of hedgehogs. Suggest how each helps hedgehogs to survive.

EVOLUTION Explain the links.

They were all part of Charles Darwin’s voyage of discovery.

Evolution - Definition Evolution is the cumulative change in the heritable characteristics of a population. What do we mean by cumulative, heritable and population?

Exam Objectives Explain the consequences of the four observations made by Darwin in proposing his theory of natural selection

Use pages 222 and 223……or RG pg 103/purple OCR 214 To answer the questions on page 4 of the booklet about Darwin’s four observations.

Charles Darwin and the theory of evolution by natural selection p4 Observations Organisms produce many offspring Members of a species vary Some variations are inherited Population size remains fairly constant Conclusions There is competition for survival Individuals which are better adapted to the environment are more likely to survive and reproduce so their genes / alleles are passed on Over time organisms may change and develop into new species (changes in genes to make new alleles are due to random mutation)

Examples of Selection Pressures Availability of suitable food Predators Diseases Physical and Chemical factors i.e. Hot and cold places

Natural selection and selection pressures Ability of xerophytic plants to survive in areas with little water 2) Camouflage and predators e.g. peppered moth and banded snails http://www.biologycorner.com/worksheets/pepperedmoth.html http://www.techapps.net/interactives/pepperMoths.swf http://www6.district125.k12.il.us/~nfischer/Moth/default.htm 3) Ability of grasses to grow roots in soil containing copper ions 4) Survival of bacteria with allele for antibiotic resistance in the presence of that antibiotic http://www.youtube.com/watch?v=zjR6L38yReE 5) Survival of humans with allele for sickle cell anaemia when infected with malaria parasite http://www.youtube.com/watch?v=1fN7rOwDyMQ

Peppered moths – evolution in action http://www. techapps Which moths survive? Why are the moths Why? different colours in different areas?

Banded snails Caepea nemoralis and camouflage

Genetic diversity Which antibiotics could be used to kill these bacteria? How does this demonstrate adaptation and natural selection? http://www.youtube.com/watch?v=zjR6L38yReE

Genetic diversity in humans Normal and sickle cell haemoglobin – adaptation and natural selection http://www.youtube.com/watch?v=1fN7rOwDyMQ

Natural Selection Read page 223. Now in pairs, write it out as a flow chart but including the terms: competition / mutation / variation / allele / phenotype / selection pressure / survival / reproduce / pass on allele / allele frequency / increases When you are happy with your chart, make a note of it. Sort the cut and stick on last page.

Natural Selection Survival of those with new allele Competition Reproduce, so pass allele to offspring. Changed characteristic Mutation/Variation (phenotype) Selection Pressure Allele frequency rises Survival of those with new allele

Exam Practice Some plants living where there is little soil water have short roots but most have an extensive root system. Can you explain this using ideas from natural selection? Answer Intra specific variation in root length Caused by a random mutation in a gene  new alleles  new phenotypes e.g. short or long roots Competition for water = selection pressure Plants with longer roots are better adapted and are more likely to survive and reproduce Allele for long roots passed to offspring and its frequency in the gene pool increases

Evolution can lead to Speciation – the formation of a new species p5 A species is a group of organisms with similar anatomical, behavioural and biochemical features which can reproduce to produce fertile offspring To produce a new species a population must become separated so it cannot reproduce / breed with the original group. It is reproductively isolated. Then the separate populations will continue to adapt to their environment so that eventually the individuals cannot produce fertile young with members of the original group. A new species has evolved. Find out the similarities and differences between the 2 ways of forming a new species = allopatric speciation and sympatric speciation (p228 text + workbook p6)

Exam Objectives Define the term speciation

Speciation - forming a new species over time. Allopatric speciation needs a geographical barrier separating populations. Sympatric speciation occurs when genetic differences appear between populations.

Speciation – pages 5 and 6 Populations must be reproductively isolated – alleles / genes cannot mix Allopatric – geographical isolation e.g. sea, river, mountain Sympatric – isolation is behavioural, biochemical, time of reproduction (spring/summer) etc Then individuals in the population adapt through random mutation to the environmental selection pressures http://www.nodvin.net/snhu/SCI219/demos/Chapter_4/Chapter_04/Present/animations/23_2_2_1.html http://www.execulink.com/~ekimmel/mixed_flash.htm

Sympatric or Allopatric ?

Finches on the Galapagos Islands p5 Common ancestor Geographical isolation on islands Random mutations  better adapted to environment e.g. beak shape and size for different foods = selection pressure Different changes on different islands Populations are eventually so different that they cannot reproduce to produce fertile offspring Allopatric speciation has occurred

Allopatric Speciation – Key Points for Exam Answers Physical barrier (isolating mechanism) separates members of a population. Selection Pressures different in 2 regions. Different alleles selected for in each region. Random Mutations. Chromosome numbers change over time, so individuals from 2 populations can no longer interbreed successfully So new species formed

3 Jackal species live in the same regions of East Africa but do not interbreed. Why not? Speciation Type? Side-striped Jackal Golden Jackal Black-backed Jackal

Sympatric Speciation – Key Points Isolating mechanism is a genetic difference between individuals. E.g. a mutation produces the wrong number of chromosomes, so offspring are infertile. A mutation produces different markings so individuals do not recognise each other as the same species.

Checking your learning What do these words mean? Species Speciation

And what do these words mean? Reproductive isolation Allopatric speciation Sympatric speciation

Why are these so important to biologists?

Evolution of the horse

Human evolution Increased brain size + becoming bipedal

Exam Objectives Discuss the evidence supporting the theory of evolution, with reference to fossil, DNA and molecular evidence Do as a table using Revision Guide/OCR book

Using DNA bases as evidence which 2 animals are most closely related Using DNA bases as evidence which 2 animals are most closely related? And which are most distantly related? Animals % difference in bases C, G, A and T in coding DNA human / chimpanzee 0.87 human / gorilla 1.04 human / orang-utan 2.18 chimpanzee / gorilla 0.99 chimpanzee / orang-utan 2.14 gorilla / orang-utan 2.25

Video – short circuit – the theory of evolution – 20 mins Evidence for evolution – page 7 http://www.youtube.com/watch?v=ewtw_nZUIDQ&feature=related whale evolution http://www.youtube.com/watch?v=yVqJ_mQazik&NR=1&feature=fvwp animal evolution + music 1) Fossils horses  increased size and the development of hooves Archeopteryx – reptile / bird (missing link) humans – increased brain size and become bipedal 2) DNA base sequence similarities suggest a common ancestor; the lower the differences the more recent the separation of the species 3) Amino acid sequence DNA codes for order of amino acids in proteins; similarities in amino acid sequences suggest evolution from a common ancestor Video – short circuit – the theory of evolution – 20 mins

Variations + Adaptations + natural selection An adaptation is a character that increases the chances of the survival and reproduction of that organism Variations between organisms in different species and between members of the same species mean that some organisms are better adapted to survive in an environment than others; this is natural selection

Exam Objectives Outline how variation, adaptation and natural selection are major components of evolution

Natural selection Variation in characteristics Selection pressure – environmental factor Some organisms more likely to reproduce than others and pass their alleles to the next generation Allele frequency in population will change if new selection pressure occurs

Some key words to use to discuss your answer: Variation Overpopulation Competition Selection pressure Adaptation Inheritance Allele frequency

Is evolution still happening? Use textbook pages 225 – 227 and revision book pages 104 – 105 to complete page 8 in workbook Try SAQs 5, 6 and 7

Is evolution still happening? P224-6

Antibiotic Resistance in Bacteria Use natural selection to explain the resistance shown by these bacteria. Make a note of it as a flow chart.

Exam Objectives Discuss why the evolution of pesticide resistance in insects and drug resistance in microorganisms has implications for humans

Is evolution still happening? page 8 Resistance to antibiotics in bacteria (selection pressure = antibiotic in environment) random mutation = change in DNA bases during semi- conservative replication (making copies of DNA) some bacteria species are now not killed by many antibiotics e.g. MRSA = methicillin resistant Staphylococcus aureus; e.g. antibiotic resistant TB http://www.youtube.com/watch?gl=GB&hl=en-GB&v=6jBD8xfbf4Y therefore scientists need to develop new antibiotics

Is evolution still happening? page 8 2) Resistance to pesticides in insects (selection pressure = pesticide in environment) a) random mutation – change in DNA bases b) more difficult to control spread of malaria if Anopheles species are resistant; for other insects, crops may fail c) chemicals can pass along food chain; use biological control – natural predators; insects not killed by pesticide pass allele for resistance to offspring; then time and money needed to develop new pesticides

Stretch and challenge Why does evolution seem to happen more quickly in microorganisms and insects than in mammals? Suggested reasons:- length of life cycle frequency of mutations variety of selection pressures

Is evolution still happening?

Finally.... http://www.becominghuman.org/ Use the website to find out what you want to know about evidence, anatomy and culture of our ancestors.

Exam Practice End of Chapter OCR1 Book on Moodle Exam Qs on Moodle under “Evolution” Past Papers F212