B4 - natural selection and genetic modification

How does ‘Ardi’ give evidence for human evolution

• The structure of her feet suggests she climbed trees

• She had long arms and short legs, more ape like

• Her brain size was the same as a chimpanzee’s

• Structure of her legs suggests she walked upright

• Hand bone structure suggests she didn’t use her hands to walk like most apes

How does ‘Lucy’ give evidence for human evolution

• Had arched feet that were adapted to walking

• Her arms and legs were and in between the length of humans and apes

• Her brain was larger than Ardi’s

• Structure of her leg and foot bones suggested she walked upright more efficiently than Ardi

How does Leakey’s discovery of fossils give evidence for human evolution

• Turkana boy - had a mixture of human and ape features, more human than Lucy

• His short arms and long legs are human like and his brain was much larger than Lucy’s

• Structure of legs and feet suggests he was better adapted to walking upright than Lucy

How do stone tools provide evidence for human evolution

• Tools progressively became more advanced as time went on

• Went from being used for cutting to evolving for weapons

What ways can you date stone tools

• Looking at the structural features of the tool, the simpler the older

• Use stratigraphy (study of rock layers), older rock layers are found below younger ones

• Using carbon dating as stone tools often have carbon containing material

How does a pentadactyl limb provide evidence for evolution

• A limb with 5 digits

• It is seen across many species

• In each species the limb has similar bone structure but a different function

• The similarity in bone structure provides evidence that species with the limb have all evolved from a common ancestor

How has genetic analysis led to the suggestion of the 3 domains instead of the 5 kingdoms

• Scientists are able to compare RNA sequences

• Found that some members of the prokaryote kingdom were not as closely related as originally thought

• Suggested the domains should be used instead

Define selective breeding

• When humans artificially select plants or animals that are going to breed so that genes for particular characteristics remain in the population

• They are bred like this so they develop useful or attractive features

What are the risks of selective breeding

• As only some alleles are selected others may become rare or disappear

• Any change in conditions (diseases) will effect all of the species bred

What did was Darwin’s theory of natural selection

• Individual organisms within a particular species show a wide range of variation for a characteristic

• Individuals with characteristics most suited to the environment are more likely to survive and breed successfully

• The characteristics that have enabled these individuals to survive are passed on to the next generation

How does antibiotic resistance support Darwin’s theory of evolution

• Because it can evolve quickly as they reproduce as a fast rate

• Some bacteria can become resistant to antibiotics

• Shows its evolution

How do bacteria develop a resistance

• A random mutation occurs in the genes of individual bacteria cells

• Some mutations protect the bacteria cell from the effects of the antibiotic

• Bacteria without the mutation die or cannot reproduce with the antibiotic present

How do fossils provide evidence for evolution

• By arranging fossils in chronological order, gradual changes in an organism can be observed

• Provides evidence for evolution as it shows how species have developed of billions of years

How have ideas about evolution have influenced modern biology

• Classification - if all living organisms have descended from a common ancestor then we are all related, organisms are classified based on how closely related they are

• Antibiotic resistance - we need to constantly develop new antibiotics to fight newly evolved bacteria resistance

• Conservation - understand the importance of genetic diversity and how it helps population adapt to environments

Define genetic engineering

A process which involves modifying the genome of an organism to introduce desirable characteristics

Describe the process of tissue culture

• A piece of a plant is placed in bleach solution to sterilise it

• A small piece of the plant is cut off and placed on sterile nutrient medium to grown

• The plant is treated with hormones so it grows roots and shoots

• When large enough they are planted into soil

State the advantages of using tissue culture in medical research

• It is easier to study how cells communicate with each other

• You can study how cancer cells spread and develop

• Investigate how cells respond to medicines

• Can be developed into tissues (e.g. trachea)

What risks do GM crops have

• Seeds for Gm plants are expensive

• Risk that GM crops could breed with wild ones and pass on resistant genes that may have unknown consequences

Explain how genetic engineering of bacteria works

• Restriction enzymes are used to cut a useful gene out of DNA

• This leaves the DNA with jagged ends called sticky ends

• If 2 sticky ends match they can be joined together using ligase