Variation

Question 1

What are inherited features?

Answer 1

Characteristics of an organism that are determined by their genes

Question 2

What are acquired features?

Answer 2

Characteristics of an organism that determined by their environment

Question 3

Inherited features can be discontinuous/discrete or continuous. What is the difference?

Answer 3

Discontinuous/discrete features have a limited range of phenotype possibilities but continuous features have a wide range of phenotype possibilities

Question 4

Does asexual or sexual reproduction create variation?

Answer 4

Sexual

Question 5

Why would a species want to reproduce asexually?

Answer 5

It is quicker to have offspring because the parent doesn’t need find a mater
If the parent is successful within their environment, it is good for the offspring to be identical to them because they are more likely to be successful

Question 6

Why would a species want to reproduce sexually?

Answer 6

Sexual reproduction creates genetically unique offspring. If the environment changes e.g. new disease, there is greater chance that some individuals might have the genetic makeup to survive and then reproduce

Question 7

What type of cell division is involved in sexual reproduction?

Answer 7

Meiosis

Question 8

What is the purpose of meiosis?

Answer 8

Type of cell division to create gametes/sex cells

Question 9

Where does meiosis occur?

Answer 9

In sexual organs - testes in males and ovaries in females

Question 10

What three processes that occur during meiosis create variation?

Answer 10

Segregation of alleles
Independent assortment
Crossing over/recombination

Question 11

Explain how segregation of alleles creates variation

Answer 11

During meiosis, only one chromosome from each homologous pair is placed into each gamete. Therefore each gamete only receives one allele from each gene and therefore gametes have unique combinations of alleles which increases variation.

Question 12

Explain how independent assortment creates variation

Answer 12

independent assortment is the random way different homologous pairs of chromosomes line up along the cell equator during meiosis. Since each gamete only contains one chromosome from each homologous pair, the gametes contain unique combinations of chromosomes and hence alleles which increases variation in the offspring..

Question 13

Explain how crossing over/recombination creates variation

Answer 13

Crossing over is when parts of homologous chromosomes and the alleles they carry are exchanged. This creates unique allele combinations in the gametes and therefore the offspring which increases variation.

Question 14

Why do each gamete e.g. sperm and an egg, are haploid - have only half the genetic information of one parent/one member from each homologous pair?

Answer 14

When the egg and sperm fuse during fertilisation is forms a diploid zygote - the chromosome number is restored and each chromosome exists as a homlogous pair. Because each gamete only provided half the genetic information from each parent, the offspring is genetically unique which increases variation.

Question 15

What other process causes variation but doesn’t necessarily occur during meiosis?

Answer 15

Mutations

Question 16

Explain how mutations create variation

Answer 16

Mutations are a change in the base sequence of DNA. This creates new alleles. This new bases sequence creates a new type of protein which creates a new phenotype hence increasing the variation in the species.

Question 17

What is a somatic mutation and why can it not be passed on to the offspring?

Answer 17

Mutation that occurs in body cells/somatic cells - not those in sexual organs involved in meiosis. Since they don’t create gametes, the mutation cannot be passed on.

Question 18

What are gametic mutations?

Answer 18

Mutations that occur in gametes and therefore can be passed on to the offspring

Question 19

Why might a gametic mutation in a parent not be visible in an offspring?

Answer 19

Might occur in a gamete not involved in fertilisation
Might produced a recessive allele that is masked in the phenotype by a dominant allele
Might code for the same amino acid as the sequence prior to the mutation so the protein still functions the same
Might change the protein’s structure but not alter its function