Topic 4: Natural Selection and Genetic Modification - PAPER ONE Flashcards
(45 cards)
Explain how bacteria can help prove Natural selection
- Bacteria can develop random mutations creating new alleles which can change characteristics. For example, a bacteria could become resistant to a particular antibiotic
- When exposed to the antibiotic, the resistant bacteria are more likely to survive than the non-resistant bacteria
- So, it will live longer and reproduce
- The allele for antibiotic resistance is therefore passed on to offspring and becomes more common in the population
How did Charles Darwin come up with his theory?
- Spent 5 years on a voyage around the world studying plants and animals on a ship HMS Beagle
- Noticed a variation in members of same species. Those with characteristics most suited to the environment were most likely to survived.
- Also noticed characteristics could be passed on to offspring
How did Wallace contribute to the theory of evolution?
- Wallace came up with the idea at the same time as Darwin (independently)
- he observed lots of evidence to help support the theory of evolution by natural selection and published his paper at the same time as Darwin
Which fossils provided evidence of Human evolution?
Ardi, Lucy, Turkana boy
What features of ‘Ardi’ provide evidence for evolution?
Fossil Hominid 4.4 million year old
- Feet structure suggests she climbed trees, had an ape-like big toe to grasp branches
- Long arms, short legs (more ape like than human)
- Brain size same as a chimpanzee’s
- Leg structure suggests she walked upright. hand bone structure suggests she didn’t use her hands to help walk (like apes do)
What features of ‘Lucy’ provide evidence for evolution?
Fossil Hominid 3.2 million years old
- Arched feet more adapted to walking than climbing, no ape-like big toe
- Size of arms and legs between apes and humans
- Brain slightly larger than Ardi’s, still similar in size to chimp’s brain
- Structure of leg bones and feet suggest she walked upright, more efficiently than Ardi
What species are Ardi, Lucy and Turkana Boy from?
Write all in italics:
Ardi - Ardipithecus ramidus
Lucy - Australopithecus afarensis
Turkana Boy - Homo erectus
What did Richard Leakey discover?
Turkana Boy 1.6 million years old
- Short arms, long legs, more like a human than an ape
- Brain size much larger than lucy’s (similar to human size)
- Structure of legs and feet suggest he was even better adapted to walking upright than Lucy
How does the development of stone tools help to prove evolution?
Stone tools gradually became more complex. This means that the brain of the different Homo species were getting larger.
How can scientists identify how old tools/fossils are?
1) Structural features: Less complex tools are likely to be older than more complex tools.
2) Stratigraphy (study of rock layers): Tools/fossils found in deeper rock layers are usually older as older rock layers are usually found below younger layers
3) Stone tools are found with carbon-containing material. Carbon-14 dating can be used to date the material
How does the Pentadactyl Limb provide evidence for evolution?
- It’s a limb with 5 digits
- In each species the pentadactyl limb has a similar bone structure for a different function e.g. human hands and bat wings
- Similarity in bone structure suggests that species with a pentadactyl limb evolved from a common ancestor
Describe the five kingdom classification system
Kingdoms (Animals, plants, fungi, prokaryote, protists) are subdivided into smaller groups…
Phylum, class, order, family, genus, species
KING PHILIP CAME OVER FOR GOOD SOUP
Why do we now use three domains rather than the five kingdoms classification method?
Technology has developed (more knowledge due to better microscopes - say this in exam):
- Woese found, using RNA SEQUENCING, that some members of the Prokaryote kingdom were not closely related
- DOMAIN THEORY BASED ON GENETICS USING GENETIC ANALYSIS
What does the three domain method of classification propose?
- He proposed that prokaryote kingdom should be split into Archaea and Bacteria
- 3 domains were created: Eukarya, Archaea, bacteria
- These domains are then subdivided into smaller groups used in the 5 kingdom system
What do each of the 3 domains contain?
Archaea: Organisms look similar to bacteria but have differences in their DNA and RNA sequences. Found in extreme places (hot springs)
Bacteria: Contains true bacteria
Eukarya: Contains broad range of organisms - fungi, plants, animals and protists
What’s selective breeding?
When humans artificially select plants or animals that are going to breed so that the genes for particular characteristics remain in the population
Explain how selective breeding works.
1) Select which characteristics you’re after from existing stock and breed them with each other
2) Select the best offspring and breed them together
4) Continue for several generations and the trait gets stronger and stronger
5) Eventually all the offspring will have the characteristic
Explain 2 uses for selective breeding
- Farmers breed together cows and bulls that are larger so they produce more meat. They can continue to do this for several generations so that the offspring will have very high meat yields.
- Rats have been bred with a strong or weak preference for alcohol so researchers can compare the effects of alcohol on their behaviour and brains to investigate the reasons behind alcoholism.
What are some disadvantages to selective breeding?
- Reduces gene pool (animals/plants closely related - inbreeding)
- Inbreeding can cause health problems as there’s more chance of organisms inheriting genetic defects when gene pool is limited e.g. heart disease in boxer dogs
- If a new disease appears many might get killed as there is little variation in the population so there’s less chance of resistance alleles being present
What’s tissue culture?
- Involves growing cells on an artificial growth medium
- Plants produced via tissue culture are clones (genetically identical). So, you can use it to created lines of clones with the same beneficial features (e.g. tasty fruit)
Explain the process of growing plants using tissue culture.
1) Chose plant to clone based on its characteristics
2) Remove several small pieces of tissue from the parent plant (best results from root or shoot tips)
3) Grow tissue in a growth medium containing nutrients and growth hormones under aseptic conditions to prevent growth of microbes
4) As the tissues produce roots and shoots they can be moved to potting compost to carry on growing
How tissue culture used for medical research?
You can investigate the effects of a substance or environmental change on the cells of a single tissue without complications from other processes in the whole organism
Explain how the tissue culture for animal cells is carried out to be useful for medical research.
1) Extract a sample of the tissue you want to study e.g. from the pancreas of an animal
2) Cells in sample are separated from each other using enzymes
3) They are then placed in a culture vessel and bathed in a growth medium containing the nutrients that they need so that they can grow and multiply
4) After several months of cell division, they can be split up again and placed into separate vessels to encourage further growth
5) Once the tissue culture has been grown, it can be stored for future use
What’s Genetic Engineering?
A process which involves modifying the genome of an organism to introduce desirable characteristics
