Variation and Evolution

Question 1

What does the phenotype of an organism depend on?

Answer 1

1) Genotype: the genes it inherits
- the combining of genes from the mother and father created genetic variation

2) Environment
- the conditions an organism grows in affects its appearance (e.g. animals- scares and plant-yellow leaves)

Question 2

An example when both genes and the environment affect characteristics:

Answer 2

Weight - the amount of food you eat (environment) and how quickly you break down food + how much is stored as fat (genes)

Question 3

How is genetic variation introduced?

Answer 3

by mutations in the sequence of DNA

Question 4

What is Evolution?

Answer 4

a change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species

Question 5

What is the Theory of Evolution?

Answer 5

All species have evolved from simple life forms that first developed more than three billion years ago

Question 6

Process of Evolution:

Answer 6

1) mutations occur which provide variation between organisms

2) the mutation could provide a survival advantage - more likely to survive to breeding age

3) mutation passed onto offspring

4) over generations, the frequency of the mutation will increase within the population

Question 7

What is speciation?

Answer 7

When evolution causes one population to become so different that they can no longer interbreed and have become a new species

Question 8

What is selective breeding?

Answer 8

When humans choose which organisms to breed in order to produce offspring with a certain desirable characteristic

Question 9

Process of selective breeding:

Answer 9

1) parents with desirable characteristics are chosen
2) they are bred together
3) select the best offspring and continue this process until all offspring have desired characteristics

Question 10

What is a problem with selective breeding?

Answer 10

It can lead to inbreeding
- breeding those with similar characteristics means it is likely they are closely related
- this reduces the gene pool as the number of different alleles are reduced
- so, if the environment changes or there is a new disease, the species could all become extinct because they have the same genetic makeup so the chance of

Question 11

What is genetic engineering?

Answer 11

Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

Question 12

How are plants and crops genetically modified?

Answer 12

plants - resistant to diseases and to produced larger fruits
crops - resistant to insects and herbicides and this will increase amount of crops produced as less will die

Question 13

How is medicine genetically modified?

Answer 13

‘gene therapy’ - to cure inherited disorders - involves transferring normal genes into patients so the correct proteins are produced

Question 14

Benefits of genetic engineering:

Answer 14

• can be useful in medicine to mass produce certain hormones in microorganisms
• can improve agriculture by improving growth, introducing modifications so crops can grow in different conditions (such as a hotter climate) and allows plants to make own herbicides or pesticides
• can create greater yields (help with world hunger)

Question 15

Risks of genetic engineering:

Answer 15

• genetically engineered crops are infertile and this gene could spread to wild plants, leading to infertility in other species which affects the entire environment
• growing with herbicides/pesticides can kill insects and other plants, which would reduce biodiversity
• people are worried we don’t understand the full effects
• GE in agriculture could lead to GE in humans - creating designer babies