Topic 7 - Genetics and Ecosystems

Question 1

What is monohybrid inheritance?

Answer 1

the two parents differ in one characteristic breed

eg. Gg and gg

Question 2

F1 offspring

Answer 2

first generation of offspring

Question 3

F2 offspring

Answer 3

second generation of offspring

Question 4

What is dihybrid inheritance?

Answer 4

the two parents differ by two characteristics breed

Question 5

What is the ratio when two dihybrid heterozygous breed?

Answer 5

9:3:3:1

Question 6

What are Co dominant alleles?

Answer 6

They are both expressed in a heterozygote.
eg. sickle cell anaemia

Question 7

Describe how epistasis can affect the phenotype of an organism.

Answer 7

• epistasis alters expression of one gene based on the presence of another gene.
• a dominant gene masks expression of a recessive gene.

Question 8

Describe how variations in alleles are.

Answer 8

Either heterozygous or homozygous.

Question 9

What does the Hardy-Weinberg principle predict?

Answer 9

The freq of alleles will remain constant, over generations providing there are no mutations.

Question 10

What is a gene pool?

Answer 10

All the alleles in a population

Question 11

Describe one way scientists can determine whether two organisms from different populations are from the same species.

Answer 11

-Breed together
- if offspring fertile then same species

Question 12

Give two features of a climax community:

Answer 12

• populations remain stable
• abiotic factors constant over time

Question 13

Describe and explain the process of succession:

Answer 13

• Pioneer species
• a species changed the conditions eg. making conditions less hostile.
• new species better competitor
• pioneer species decreases new species increases

Question 14

Two conditions for mark - release - capture investigations to be valid:

Answer 14

• marking does not affect survival eg. predation
• no breeding in the population

Question 15

Why do the species present change during succession?

Answer 15

• species change the environment conditions (less hostile)
• other species better competitors

Question 16

Describe how you could estimate the size of a population of a particular plant species in an area.

Answer 16

• use a grid to divide area into sections
• use a random number generator
• count freq in these randomly generated quadrants
• use a large sample to calculate the mean number of plants per quadrant

Question 17

What is meant by uniformly distributed?

Answer 17

organisms are equally spread

Question 18

How do assumptions made in proportional sampling differ from those made in mark-release-recatpure?

Answer 18

in mark release recapture:
- no assumption that organisms uniformly distributed
- size of total area not required

Question 19

Give one assumption that is made in both proportional sampling and mark-release-recapture:

Answer 19

• animals are all part of same population

Question 20

In genetic crosses, the observed phenotypic ratios are often not the same as expected ratios. Why?

Answer 20

• small sample size
• fertilisation of gametes is random
• epistasis
• linked genes

Question 21

Causes of genetic variation in organisms:

Answer 21

• mutations
• crossing over
• random fertilisation of gametes
• independent segregation of homologous chromosomes

Question 22

What is meant by the term phenotype?

Answer 22

Expression of characteristic due to genetic constitution and environment.