Variation and Evolution - Topic 6

Question 1

What is variation?

Answer 1

It is all the differences in characteristics of individuals in a population.

Question 2

What are some of the factors that lead to variation?

Answer 2

1. Alleles inherited (Genetic Variation)
2. Environment
3. Genes and environment.

Question 3

What is there a lot of in a population? (in terms of variation)

Answer 3

Genetic variation due to mutation.

Question 4

How do mutations interact with the phenotype? (3 points, 2 examples)

Answer 4

Some Mutations will influence a phenotype (height with good diet)
A few mutation will determine a phenotype (eye colour)
Vary rarely, some mutation can lead to a new phenotype.

Question 5

How can a mutation leading to a new phenotype be beneficial?

Answer 5

If the environment changes, it could cause a rapid change in species.

Question 6

What is Evolution?

Answer 6

It is the idea that all living things have evolved from simple life forms.

Question 7

‘Rabbits have a different combination of alleles, the environment gets colder, explain how this can benefit certain rabbits’ (4 marks) (How does this demonstrate natural selection)

Answer 7

1. Some rabbits will have alleles for thicker fur, others will have alleles for thinner fur.
2. If the environment gets colder, rabbits with alleles for thicker fur are more likely to survive.
3. So, thicker fur rabbits are more likely to reproduce and produce offspring with the allele for thicker fur, they survive and also reproduce - natural selection.

Question 8

How can new species be formed by natural selection?

Answer 8

Sometimes, two populations of one species can become so different in phenotype they can no longer interbreed, so they become two different species.

Question 9

‘Describe the process of selective breeding to produce large cows for meat’ (4 marks)

Answer 9

1. Mixed population of cows and we select the largest male and female.
2. Breed them together.
3. Offspring will be a mixture of large and small animals due to variation
4. We not select the largest male and female offspring and breed them.
5. Continue over man generations until offspring are large.

Question 10

Why have domestic dogs, food crops, cows and certain plants been selectively bred?

Answer 10

1. Domestic dogs - to have a gentle nature.
2. Food crops - to be resistant to disease.
3. Cows - Produce more meat/milk.
4. Certain plants - large or unusual flowers.

Question 11

What are the benefits of selective breeding? What are the problems?

Answer 11

Benefit
1. Higher food production
2. Desirable traits.

Problem
1. Can lead to inbreeding, and can cause greater risk of inherited defects.
2. Ethical concerns.

Question 12

‘Describe the process of genetic engineering’ (4 marks)

Answer 12

1. Identify the gene we want to transfer.
2. Enzymes used to isolate the gene.
3. Transfer gene to a small circle of DNA called plasmids, or a virus (vectors)
4. Desired gene is transferred to target organism.

Question 13

Why have plant crops been genetically engineered?

Answer 13

To produce a higher yield, and we can make them resistant to disease, or to produce peter crops.
Some are resistant to herbicides, farmers can kill weeds without harming crops.

Question 14

Why have bacterial cells been genetically modified?

Answer 14

To contain the human insulin gene, bacteria produces insulin so can be used to treat type 1 diabetes.

Question 15

Why do some people have ethical objections to genetic engineering?

Answer 15

1. Some people think it could be harmful to insects and flowers, we need to research more.
2. Long term effects are not known for gene therapy.

Question 16

What is gene therapy?

Answer 16

Uses genetic modification for inherited disorders.

Question 17

What is the advantage of cloning?

Answer 17

• We know the exact characteristic it will be.

Question 18

‘Describe the process of cloning a plant by taking cuttings.’ (3 marks)

Answer 18

1. Small piece of plant is removed.
2. End is dipped in rooting powder, which contains plant hormones and encourages growth.
3. We have now made them genetically identical.

Question 19

‘Describe the process of cloning plants by tissue culture’ (4 marks)

Answer 19

1. Take a plant, divide into hundred of tiny pieces which contains cells.
2. The small groups of cells are incubated in plant hormomes.
3. Plant hormone stimulate cells to grow and become clones.
4. Sterile conditions so no microorganisms can be introduced.

Question 20

What are the advantages of cloning plants?

Answer 20

1. Used in commercial plant nurseries - thousands can grow quickly and be clones.
2. Used to preserve rare species of plants.

Question 21

‘Describe the process of cloning horses by embryo transplanting (5 marks)’

Answer 21

1. Sperm and egg collected from horses with desirable characteristics.
2. Fertilisation occurs, produces a fertilised egg.
3. Fertilised egg develops into a early embryo.
4. Use a glass rod to split the embryo into two.
5. Transplant two embryo into host mothers for it to grow.

Question 22

‘Describe the process of adult cell cloning (5 marks)’

Answer 22

1. Remove a cell from the animal we want to clone.
2. Remove nucleus from cell.
3. Take an unfertilised egg cell from same species, throw the nucleus away.
4. Insert nucleus into original adult body cell into empty egg cell.
5. Egg cell gets an electric shock, cell divides to form an embryo.
6. When embryo has developed into ball of cells, it is inserted into female womb.

Question 23

What are the advantages of embryo/adult cell cloning? What are the disadvantages?

Answer 23

Advantages
1. Medical benefits.
2. Preserving endangered species.

Disadvantages
Ethical objections, destruction of embryos.

Question 24

Who proposed the theory of evolution by Natural Selection?

Answer 24

Charles Darwin.

Question 25

What is the theory of evolution by natural selection (3 points)

Answer 25

1. We can see a wide range of genetic variation for every characteristic. 2. Characteristics are most suited to the environment are most likely to survive. 3. Characteristics are passed onto the next generation.

Question 26

What did Darwin publish in 1859? Why was this controversial?

Answer 26

'On the Origin of Species' 1. A lot of people believed in god creating earth and animals, Darwin was challenging this. 2. Many scientist thought that he did not have enough evidence. 3. People did not understand that characteristics are inherited.

Question 27

What did Jean Baptiste Lamarck propose? Why was his theory a problem?

Answer 27

He proposed that when a characteristic is used regular, it becomes more developed, and this strengthened characteristic is passed onto the offspring. We now know that in the vast majority of cases this type of inheritance cannot occur and that Lamarck’s ideas were incorrect.

Question 28

What was Alfred Russel Wallace interested in? What did he independently propose? Who did he jointly publish their findings with?

Answer 28

He was interested in the warning coloration of animals, and wanted to know how it evolved. He independently proposed Evolution by Natural Selection, and in 1858 Darwin and Wallace both published their findings.

Question 29

What did Wallace notice about species?

Answer 29

He noticed that closely related species were separated by geographical barriers.

Question 30

'Describe how a new species of snail forms (6 marks')

Answer 30

1. An island containing one species of snails can all interbreed, and mutations will benefit them. 2. River separates the snail into two groups, geographical barrier. 3. No interbreeding between the two groups of snails. 4. Overtime, natural selection will favour different alleles on the two sides of the island (food source) 5. No mutations can spread due to no interbreeding, population of snails will change over time. 6. If they remix, phenotype so different that they can no longer interbreed, so different species.

Question 31

What did Gregor Mendel study?

Answer 31

He studied how characteristics were passed on between generations of plants, and breeding experiments on them.

Question 32

What was one of Gregor Mendel's observations?

Answer 32

That characteristics are determined by inherited units, and that these units do not change when passed down onto descendants.

Question 33

Why was Mendel's work not noticed until after his death?

Answer 33

When he was alive, scientists did not understand his theory, and he was forgotten. And, There was no knowledge of the mechanisms behind his findings (DNA, genes and chromosomes had not been discovered yet).

Question 34

What occurred in the late 19th century, - early 20th century that was a key discovery to genetics? How did this link to Mendel?

Answer 34

1. The behaviour of chromosomes during cell division was observed 2. Mendel’s ‘hereditary units’ were realised. 3. Scientists believed Mendel’s ‘units’ must be located on chromosomes

Question 35

What occurred in 1953 that contributed to genetics? What did this lead too?

Answer 35

Structure of DNA was determined, leading to gene theory.

Question 36

What do fossils provide us with? What are they?

Answer 36

They provide us with evidence for evolution. And they are the remains of organisms from millions of years ago which are formed in rocks.

Question 37

What are the three ways fossils form?

Answer 37

1. Parts of organisms have not decayed (conditions for decay are absent.) 2. Can form even if decays, if parts of organisms are slowly replaced by minerals during the decay process. 3. Can be the preserved tracks of organisms.

Question 38

Why can scientists not be certain on how life on earth began?

Answer 38

1. Because many of the earliest life forms were soft bodied organisms, these organism vary rarely formed fossils, and if they did they were destroyed.

Question 39

What does extinction mean?

Answer 39

No remaining individuals of the species are still alive.

Question 40

What are the 4 reasons for extinction?

Answer 40

1. Catastrophic Event 2. Environmental Changes. 3. New disease and pathogens. 4. If a new more successful species evolve and competes with it.

Question 41

Why are bacteria able to evolve rapidly?

Answer 41

Because they can reproduce every 30 minutes.

Question 42

How do antibiotic strains of resistance arise?

Answer 42

Certain strains of antibiotics are not killed, these evolve and antibiotic resistance occurs, common strain being MRSA.

Question 43

'Describe how Antibiotic resistance can arise (4 marks'

Answer 43

1. Population of bacteria are pathogens. 2. Due to genetic variation, one bacteria could have a mutation, which leads to antibiotic resistance. 3. If we use an antibiotic all bacteria are killed by the resistant one stays. 4. So, antibiotic resistance strains survives and reproduces. 5. Population of resistant bacteria rises, now spreads due to no effective treatment, and people are no longer immune.

Question 44

What are the 3 ways we can reduce antibiotic resistance?

Answer 44

1. Doctors should not prescribe them inappropriately. 2. Patients should complete whole course of them, so they are all killed. 3. Restrict use of antibiotics in farming.

Question 45

What do developing new antibiotics take? And why can they not keep up with new resistance?

Answer 45

Takes time and money to create, and as resistant strains take place all the time, it is unlikely they can keep up.

Question 46

How did Carl Linnaeus start to classify species by?

Answer 46

Into different categories based on structure and characteristic. He divided them into two kingdoms, animals and plants.

Question 47

What were the smaller categories that Carl classed them into? What is the eunomic we can use to remember it?

Answer 47

Kingdom Phylum Class Order Genus Species King Prawn Curry of Fat Greasy Sausages.

Question 48

What is the binomial naming system?

Answer 48

It is the genus + species together which gives them there name, and it based on what we can see.

Question 49

How has developments in biology impacted the classification system?

Answer 49

We can use microscopes for internal structures, and organisms biochemistry. This led to the three domain system by Carl Woese.

Question 50

What does the three domain system contain?

Answer 50

1. Arceha, which are primitive bacteria found in extreme environments. 2. True Bacteria, e.g human digestive system 3. Eukaryota, animals plants fungi and protists.

Question 51

What are Evolutionary Trees used to show? What do they use to make them?

Answer 51

They show the relations between organisms, they use classification data, or fossils for extinct organisms, but the issue is we have incomplete fossil records.