Topic 4- Natural selection and genetic modification

Question 1

Explain natural selection

Answer 1

1. Organisms show genetic variation
2. Selection pressure- comes competition for food and resources
3. The ones that have adapted have more chances of survival , so the fittest survive.
4. This means that these alleles are passed on that have adapted to the selection pressure
   5.Then this gene becomes more common in the population over time.
   5

Question 2

Explain how bacteria provides evidence for evolution

Answer 2

Bacteria becomes resistant to antibiotics so the allele for the antibiotic resistance is passed on

Question 3

Explain how fossils provide evidence for evolution

Answer 3

We can place fossils in chronological order and observe how they changed and developed over time.

Question 4

Describe Wallace’s role in developing the theory of evolution by natural selection

Answer 4

He provided evidence for natural selection and worked with Darwin to develop the theory

Question 5

Describe Ardi as a fossil hominid:

Answer 5

1. The structure of her feet suggested she climed trees
2. She had long arms and short legs
   (4. 4 million years ago)

Question 6

Describe Lucy as a fossil Hominid

Answer 6

1. Arched feet so more adapted to walking
2. Brain size was slightly larger than Ardi
   (3. 2million years ago)

Question 7

Leaky fossil hominids

Answer 7

Leaky and his team went to Kenya.

1. They found the Turkana boy- 1.6 million year old , with short arms and long legs and similar human brain size.

Question 8

What is a pentadactyl limb?

Answer 8

limb with 5 digits

Question 9

State one method the scientists could use to find out the age of the stone tool.

Answer 9

using statigraphy- study of the rock layers

Question 10

The 5 kingdoms

Answer 10

Kingdom
Phylum
Class
Order
Family
Genes
Species

Question 11

Give one example of how advances in technology allowed scientists to distinguish between Archea and Bacteria

Answer 11

RNA / DNA sequencing showed that archea and bacteria were less closely related than first thought

Question 12

Explain what is selective breeding:

Answer 12

(its is breeding the best plants and animals to produce the best possible offspring)

1. From your existing stock select the the ones which have your required characteristic.
2. Breed them with each other
3. Select the best of the offspring and breed them.
4. Continue this process over several generations , so the desirable characteristic becomes stronger.

Question 13

Why is selective breeding useful?

Answer 13

1. Its important for agriculture - to produce more meat and milk (larger size)
2. Medical research - investigating alcoholism

Question 14

potential problems selective breeding can cause

Answer 14

1. reduces gene pool
2. Inbreeding can cause health problems (most pugs have breathing problems)
3. Serious problems may occur if a new disease appears, as there is less chance of resistant alleles being present.

Question 15

A farmer discovers an apple tree in his orchard that produces new kind of apples. Describe the method of tissue culture he could use to make clones of this tree.

Answer 15

Remove pieces of fast growing regions . Then place it in the growth medium containing nutrients and growth hormone under aseptic conditions.Once roots and shoots have grown place in the compost to allow to grow further.

Question 16

Explain how enzymes can be used to cut up DNA and join the pieces together

Answer 16

1. Restriction enzymes recognise the specific sequence of DNA and cut the DNA. This leaves sticky ends.
2. Ligase enzymes are then used to join two pieces of DNA at their sticky ends
3. Two different pieces of DNA stuck together are known as recombinant DNA

Question 17

Explain a benefit of being able to genetically engineer herbicide-resistant crops.

Answer 17

It can improve the yield of the crop because herbicide-resistant crops can be sprayed with herbicides to kill weeds without the crop being damaged.

Question 18

Suggest three ways that could be used to help provide food for a growing human population

Answer 18

1. improve yields
2. use fertilisers on poor soil
3. use of biological pest control