GCSE Inheritance, Variation and Evolution

Question 1

Give an overview of sexual reproduction

Answer 1

Involves two parents that produce male and female gametes that fuse during fertilisation. Meiosis is used to make these gametes with 1/2 the number of chromosomes. Fertilisation causes the haploids to fuse and form a diploid zygote. Offspring have genetic variation from different combinations of alleles.

Question 2

Give an overview of asexual reproduction

Answer 2

Involves one parent producing a clone of themselves via mitosis with the same number of chromosomes as the original parents. Offspring have no genetic variation and are genetically identical.

Question 3

Give examples of sexual reproduction

Answer 3

Multicellular animals, tomatoes, oranges

Question 4

Give examples of asexual reproduction

Answer 4

Yeast, amoeba, daffodil bulbs, potato tubers

Question 5

What are the advantages of sexual reproduction?

Answer 5

Produces genetic variation in offspring, variation provides species with increased long term survival, selective breeding can speed up natural selection

Question 6

What are the advantages of asexual reproduction?

Answer 6

Only 1 parent needed, more time & energy efficient, often produced in favourable conditions, often well adapted to environment + can easily colonise area

Question 7

What are the disadvantages of sexual reproduction?

Answer 7

Time consuming to find a mate, energy needed to produce gametes, fewer offspring produced more slowly

Question 8

What are the disadvantages of asexual reproduction?

Answer 8

Results in lack of competition in ecosystem (extinction more likely), cannot produce multicellular animals, limits evolutionary potential.

Question 9

Define mitosis

Answer 9

the division of the nucleus of the cell to produce 2 new daughter nuclei (and therefore 2 new cells) that are genetically identical to the parent cell.

Question 10

When does meiosis occur?

Answer 10

In sex organs to produce gametes for sexual reproduction

Question 11

What is the start code for mRNA?

Answer 11

AUG (met)

Question 12

What are the end codes for mRNA?

Answer 12

UAA, UAG, UGA

Question 13

What is DNA made up of

Answer 13

Alternating sugar-phosphate strands connected by complimentary bases (T&A, C&G)

Question 14

What are genes?

Answer 14

Sections of chromosomes that code for proteins.

Question 15

What are chromosomes?

Answer 15

Long strands of DNA divided into genes.

Question 16

How many pairs of chromosomes do humans have?

Answer 16

23

Question 17

Why are chromosomes found in pairs?

Answer 17

One chromosome comes from each haploid sex cell to fuse during fertilisation.

Question 18

What is a mutation?

Answer 18

A change in the DNA base sequence.

Question 19

What can the human genome project be used for?

Answer 19

Study of genes linked to disease, considers likelihood of developing genetic disease, finds treatment for hereditary disease, traces human migratory patterns

Question 20

What are the disadvantages of the HGP?

Answer 20

Ethical concerns: prejudice against certain genomes.

Health insurance companies might charge people w certain genomes more than others

Question 21

How many different amino acids are there in the body?

Answer 21

20

Question 22

How does DNA coding for protein synthesis reach the ribosomes?

Answer 22

mRNA is created.

Question 23

What is mRNA?

Answer 23

A tiny molecule of single-stranded DNA with exposed bases that can fit through the pores in the nuclear envelope. It has base U instead of base T.

Question 24

Describe the process of transcription in protein synthesis.

Answer 24

The DNA is ‘unzipped’ by DNA polymerase. A single

Question 25

How might two different species evolve? (speciation)

Answer 25

• Two ancestral populations are separated by a geographical barrier. (isolation mechanism - islands)
• There is already genetic variation within this separated population (beak size and shape)
• In different environments (food source), natural selection occurs and causes the best adapted species (best beak) to survive and reproduce.
• This causes the advantageous allele to be passed onto offspring in each individual population (develops into new species)

Question 26

When does extinction happen?

Answer 26

When the last living member of a species dies and the species ceases to exist.

Question 27

What is an endangered species?

Answer 27

A species that is at risk of going extinct.

Question 28

What are the three types of extinction?

Answer 28

Direct, indirect and natural

Question 29

What is direct extinction?

Answer 29

When humans destroy so many animals/plants that they cease to exist.

Question 30

What is indirect extinction?

Answer 30

Humans affect a habitat so much that it causes population to fall.

Question 31

What is natural extinction?

Answer 31

When a species declines in numbers gradually but steadily at the end of its evolutionary period (speciation)

Question 32

How did dodos go extinct?

Answer 32

They were flightless and ground-nesting. Humans brought pigs and rats to the island and preyed on the dodo’s eggs. The dodo could not adapt to these new conditions, so less were born and went extinct in 1660.

Question 33

What are the five kingdoms?

Answer 33

bateria, protist, fungus, animal, plant