Topic 4 - Natural Selection & Genetic Modification

Define: Evolution

Gradual change in a species over time.

Which scientist believed evolution occurs by natural selection?

Charles Darwin.

Did Darwin and Wallace have the same or different ideas relating to the theory of evolution? What were their theories?

They had the same theory of evolution by natural selection.

Pick A, B, C or D.

A - Charles Darwin.

D - New species evolve over many generations.

Suggest two possible reasons why animals to the west of the Wallace line are different from animals to the east of the Wallace line.

• Different environments/climate/habitats/ecosystems.

• Different mutations.

• Different selection pressure.

• Different prey and predators.

• Different diseases present.

Give one reason why the work of Alfred Wallace encouraged Charles Darwin to publish his theory of evolution.

• More evidence.

• He showed that animals have adapted to their environments and evolved from common ancestors.

Describe the role of Wallace in the development of the theory of evolution by natural selection.

Proposed a theory of natural selection that was similar to Darwin’s but with more evidence to support the theory.

How has the work of Darwin and Wallace impacted modern biology?

• Classification of organisms can now be done on the basis of evolutionary relationship.

• Conservationists know that it is important to preserve genetic variation in habitats so that populations can adapt to change.

• Microbiologists understand how antibiotic resistance develops and can take steps to reduce the risks. It is now important to finish antibiotic treatments and increases the need for the production of new antibiotics

Describe the role of Wallace in the development of the theory of evolution by natural selection.

Proposed a theory of natural selection that was similar to Darwin’s but gathered greater evidence to support the theory.

What is natural selection?

Organisms within a species with certain characteristics are more likely to survive than others as they are better suited to their environment. This means that they have the beneficial allele.

Does natural selection require a population to be genetically identical or varied in order to occur?

Genetically varied.

Describe the theory of evolution by natural selection.

• Organisms in a species have genetic variation.

• There is a selection pressure such as change in environment or diseases.

• Random mutation gives an organism a selective advantage.

• These organisms adapt to survive and then reproduce to pass on their beneficial alleles/characteristics to the offspring.

• Repeated over many generations so frequency of advantageous allele increases.

Which mnemonic do we use to answer a question about natural selection?

G enetic variation.

E nviromental change.

N atural selection.

I nheritance.

E volution.

Describe how the thinner beak of species A is as a result of evolution.

• Variation in beak shape/mutations occurred that changed the shape of the beak.

• Thinner beaks are more suited to catching insects for food.

• Birds with thinner beaked are more likely to survive because they can obtain more food than those with thicker beaks.

• Birds with thinner beaks reproduce and pass on alleles for thinner beaks.

• Occurs over many generations until all birds have thin beaks.

Explain how natural selection could have caused an increase in beak length because of the use of bird feeders.

• Population of great tits show variation where some birds have longer beaks.

• Bird feeders exert a selection pressure.

• Birds with longer beaks are more likely to survive because they can obtain more food than those with shorter beaks.

• Birds with longer beaks reproduce and pass on alleles for long beaks to their offspring.

• Occurs over many generations so the beak length of the bird population increases.

Darwin believed that male birds have feathers that are brightly coloured to make them more attractive to female birds. Wallace thought that female birds have feathers that are less brightly coloured so they are more likely to survive.

Explain why having feathers that are less brightly coloured increases the survival rate of females.

• Fewer bright feathers are less noticeable and makes it easier for birds to camouflage.

• Therefore they are less likely to be eaten by predators and may find it easier to get food from their prey.

Darwin believed that male birds have feathers that are brightly coloured to make them more attractive to female birds. Wallace thought that female birds have feathers that are less brightly coloured so they are more likely to survive.

Suggest why it is important for type survival of the species that survival rate is higher in female birds that males.

Female birds lay eggs to produce offspring whereas males do not reproduce. Therefore, even if lots of males die, one male can still reproduce with many female birds.

In Tanzania, more than 30 elephants a day are killed by poachers, who tear out the tusks and sell them (usually illegally). In the past century, it has been noted that some African elephants have not developed tusks in their lifetime. Suggest why some African elephants have stopped developing tusks.

• There is variation within the population.

• The selection pressure is the poachers that hunt elephants for their tusks.

• The elephants without tusks are more likely to survive, reproduce and pass on the allele. This is repeated over generations.

Why did many people doubt Charles Darwin’s theories?

• It challenged the belief that God created all living things.

• Little evidence - not many fossils + no knowledge of antibiotic resistance.

• Little understanding of genes, inheritance etc.

Identify two factors contributing to the gradual acceptance of Darwin’s theory of evolution.

• Challenges to religious beliefs.

• Evidence like fossil discoveries.

Why does competition between organisms in a habitat exist?

Resources required for survival are limited.

Give examples of competition between organisms within a habiat.

• Animals - Food, shelter, mates etc.

• Plants - Light, water, minerals etc.

There are several sources that provide evidence for evolution such as selective breeding. Give more examples.

• Antibiotic resistance in bacteria.

• Similar bone structures across species like the pentadactyl limb.

• Fossils and discovery of different tools.

Define: Classification

Organising living things into groups according to similar characteristics.

What is taxonomy?

Classification of organisms into taxa; kingdom, phylum, class, order, family, genus, species.

Name the 7 groups to classify animals into from largest to smallest.

Kingdom, Phylum, Class, Order, Family, Genus, Species.

Name the 7 groups to classify animals into from smallest to largest.

Species, Genus, Family, Order, Class, Phylum, Kingdom.

What is the mnemonic to remember kingdom, phylum, class, order, family, genus and species?

King Phillip Came Over From Great Spain.

What happens not the number of organisms in each taxonomy as you move down the hierarchy?

Decreases.

Traditionally, organisms were grouped based on similarities and differences in their anatomy and behaviour. What is the problem with this?

Organisms that are not closely related may look alike or behave similarly if they live in the same environment whilst some closely related species may look very different because they live in different habitats.

Define: Species

A group of similar organisms that can breed to produce fertile offspring.

Name the 5 kingdoms organisms can be organised into

Animal, Plant, Fungi, Bacteria/Prokaryotes, Protist.

Name the 3 domains organisms can be organised into

Archaea, Bacteria, Eukarya.

Which domain contains ancient bacteria?

Archaea.

Which domain contains true bacteria?

Bacteria.

Which domain contains animals, plants, fungi and protists?

Eukarya.

Which domain do eukaryotic organisms belong to?

Eukarya.

Which domains do prokaryotic organisms belong to?

Archaea and bacteria.

Birds are classified in the domain Eukarya. Why are the cells from birds described as eukaryotic?

A - Membrane bound organelles.

What is the name of the domain that plants belong to?

Eukarya.

Is the domain or kingdom system more accurate? Why?

Domains because it uses genetic analysis to show the similarities and relationships between animals.

Give one reason why the three domain classification system was proposed.

• It uses improved genetic and chemical analysis.

• Based on genetics and DNA which shows that DNA of archaea is more similar to DNA of eukaryotes than prokaryotes.

Scientists can sequence genes from different organisms. Describe how this type of enteric analysis provides evidence for evolution.

Compares the genes of different organisms. Closely related organisms have similar sequences to show evolution.

B.

Describe organisms in the animal kingdom.

Multicellular, Nuclei, No cell wall, Eat other organisms.

Describe organisms in the plant kingdom.

Multicellular, Nuclei, Cellulose cell wall, Makes food via photosynthesis.

Describe organisms in the fungi kingdom.

Mainly multicellular but some such as yeast are unicellular, Nuclei, Chitin cell wall, Digest dead materials.

Describe organisms in the bacteria kingdom.

Unicellular, No nucleus, Cell wall.

Describe organisms in the protist kingdom.

Mainly unicellular, some multicellular, Some have cell walls.

Who is the oldest human fossil and how old are they?

Ardi; 4.4 million years old.

How old is Ardi?

4.4 million years old.

How was Ardi similar to humans?

Walked upright + leg structure is human like.

How was Ardi similar to apes?

• Shorter legs and longer arms than humans.

• More body hair.

• Shorter.

• Smaller head.

• Ape like big toe.

Describe the fossil of Ardi.

• Shorter legs, smaller head and longer arms than humans.

• More body hair.

• Shorter.

• Ape like big toe.

• Similar leg structure to humans.

• Walked upright.

Describe the evidence that scientists may have used to show that Ardipithecus ramidus inhabitated the Earth earlier than Homo habilis.

• Looked at differences in the structural features of the fossil.

• Ardipithecus ramidus would be deeper in the rock than Homo habilis.

How old is Lucy?

3.2 million years old.

How is Lucy evolved more recently than Ardi?

• Walks more upright than Ardi and structures of feet/legs more adapted for walking over climbing.

• More human like feet - smaller, arched, no ape like big toe.

• Limbs more similar in length to humans than Ardi.

• Small head still but slightly bigger than Ardi.

• Younger fossil.

From which continent did humans evolve from?

Africa.

Order the human fossils from oldest to newest.

• Ardi.

• Lucy.

• Homo habilis.

• Homo erectus.

• Homo sapiens.

Suggest an explanation for the extinction of Homo habilis.

• Likely to be outcompeted by the Homo erectus.

• Struggled to survive due to the presence of a new selection pressure like environmental change or disease.

Who discovered fossils from 1.6 million years ago in Africa?

Leakey.

What did Leakey discover?

Fossils in Africa from 1.6 million years ago.

What are the common evolution trends in humans?

• Decease in body hair.

• Decrease in limb size/proportion.

• Increase in height.

• Increase in skull volume.

Describe the structural changes that have occurred during human evolution.

• Skull volume has increased.

• Walking upright.

• Taller.

• Shorter arms and longer legs.

Around 2 million years ago, Homo erectus (an ancestor of today's humans) evolved. Its predecessor was Homo habilis. Homo erectus is believed to be the first human-like species to have stood predominantly on its back legs.

Suggest and explain an advantage for Homo erectus to be able to stand predominantly on its back legs.

The ability to see further by being taller to spot prey/predator.

Homo habilis was succeeded on Earth by Homo erectus. The two species coexisted on Earth for around 400 000 years before Homo habilis became extinct. Suggest one reason for the extinction of Homo habilis.

Outcompeted by Homo erectus for food/water/shelter as Homo erectus was more intelligent.

Are rock layers containing older rocks found closer or further away from the Earths surface?

Further away.

Are rock layers containing newer rocks found closer or further away from the Earths surface?

Closer.

Does older or newer rock contain simpler organisms?

Older.

Does older or newer rock contain more complex organisms?

Newer.

Will more complex tools be found in older or newer rock?

Newer.

What type of tools are found in newer rock?

Complex, sophisticated, sharp, specialised tools.

Will more simple tools be found in older or newer rock?

Older.

What type of tools are found in older rock?

Simple, blunt tools.

Explain which stone tool was most likely to be used by Homo erectus.

Stone tool B because it is more sophisticated and sharper. Home erectus lived the most recently out of all fossils.

Describe how tool P was made.

By hitting it with another rock/something hard to knock flakes and chips off.

A scientist stated that tool Q was made by a more evolved human ancestor than tool P. Suggest why.

Tool Q is sharper/more pointed than tool P.

Give one reason why scientists believed that tool Q was used by a more recent human ancestor.

It is more sophisticated and sharper.

If a fossil is found in a 200,000 year old rock, how old is the fossil?

200,000 - always the same age.

Describe the ways that stone tools and fossils can be dated to find out how old they are.

• Using the age and layer of sediments and rock where the tool is found to indicate the tools age.

• Compare to other finds of known age from the same layer of rock.

• Compare with other tools/fossils that have already been dated.

• Radiometric dating.

• Carbon dating.

Explain how the information in Figure 15 provides evidence for human evolution.

Age of tools - Younger rock layers towards top and older rock layers lower down so C is older than B which is older than A. Rocks can be dated by radiometric dating.

Quality of tools - A is the most sophisticated/specialised/ refined. C most basic/simple and less sophisticated. B shows some evidence of being worked but is still rough.

Skills and intelligence - Recent tools like A show that humans have greater human manipulation, greater skill and higher intelligence compared to when C was made.

What do discoveries of stone tools show about human evolution?

Humans have become more intelligent over evolutionary time; more recent tools tend to be more advanced, indicating the evolution of more complex brain function

Give one method that can be used to date a fossil of a Hipparion.

• Radiometric dating.

• Location in rock layer.

• Age of fossils surrounding it.

Give one reason why scientists have concluded that the modern horses evolved from Hipparion.

They have a similar pentadactyl limb structure.

What is the name given to the type of structure shown?

Pentadactyl limb.

What is a pentadactyl limb?

A limb with 5 units.

How does many species having a pentadactyl limb prove evolution?

Despite looking externally different; this similarity in bone structure shows that they all evolve from the same species or have a common ancestor. They have now adapted the pentadactyl limb for different purposes.

Describe one difference between the humerus of the whale and human.

The whale humerus is shorter and wider.

Describe one difference between the phalanges of the horse and human.

The horse has fewer phalanges with 3 whereas the human has 14. The horse also has thicker phalanges.

Describe how the structure of these limbs provides scientists with evidence for evolution.

They have a pentadactyl limb to suggest a common ancestor. This limb structure has been adapted for different functions.

Describe the reasons why the anatomy of the pentadactyl limb suggests that bats and cats evolved from a common ancestor.

Same bone structure is unlikely to have occurred more than once during evolution, suggesting that they have a common ancestor.

Genetic analysis provides evidence for evolution. Scientists can sequence genes from different organisms. Describe how this type of genetic analysis provides evidence for evolution.

Scientists can compare the DNA sequences of different organisms. Species that are closely related have more similarities in their DNA and gene sequences, showing that they share a recent common ancestor.

Fossils can provide evidence of evolution. Explain why the fossil record is incomplete.

• Only hard tissues/bones form fossils; not soft ones.

• Many fossils haven’t been found yet or only fragments may be found.

• Fossils may be damaged by natural causes.

Describe the evidence that scientist might have used to show that certain species inhabited the earth earlier than others.

Structural features of fossils and depth in rock layer.

Suggest an explanation for the extinction of fossils like Homo Habilis.

Outcompeted by previous species due to the new selection pressure.

What is antibiotic resistance?

The ability of bacteria to withstand the effects of an antibiotic.

What results in antibiotic resistance in bacteria?

Mutations in bacterial DNA.

Explain how bacteria can become resistant to antibiotics.

• Genetic variation exists due to mutations, which can give some bacteria antibiotic resistance.

• Antibiotics are introduced to an environment, acting as a selection pressure.

• The bacterium better adapted and more resistant survives, whilst others are killed.

• High resistant bacteria will breed and divide, passing on their beneficial, resistant allele to the offspring.

• This occurs over many generations until only resistant individuals remain, increasing frequency of antibiotic resistant allele. Now antibiotics don’t work as all bacteria is highly resistant to it.

How does the development of antibiotic resistance provide support for Darwin's theory of evolution by natural selection?

Bacteria reproduce and divide rapidly so characteristics are quickly passed on, allowing natural selection to be observed over a short time period.

Why is the development of antibiotic resistance in bacteria a good study for evolution?

Bacteria reproduce very rapidly so evolution can easily be observed.