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Question 1

Define abiotic factor

Answer 1

> Non-living, physical conditions in an ecosystem

>Example: temperature, light, soil conditions and pH

Question 2

Define adaptation

Answer 2

> An individual increases their chances of survival + reproduction
By altering / adjusting structure / habits, often occuring through natural selection

Question 3

Define allele

Answer 3

A different version of a gene

Question 4

Define allele frequency

Answer 4

How often an allele occurs in a population

Question 5

Define autosomal-linkage

Answer 5

Two or more genes with loci on the same autosome (i.e. not a sex chromosome)

Question 6

Define biotic factors

Answer 6

> Effect of activities of living organisms on other organisms

>Example: food availability, predation and competition

Question 7

Define carrying capacity

Answer 7

Maximum number in a population that can be sustainably supported in an ecosystem

Question 8

Define climax community

Answer 8

Fairly stable, final community at the end of succession

Question 9

Define codominant

Answer 9

Alleles that are both expressed in the phenotype i.e. neither is recessive

Question 10

Define ecological niche

Answer 10

> The role of a species within its habitat

>Governed by adaptation to both abiotic and biotic conditions

Question 11

Define epistasis

Answer 11

The allele of one gene masks the expression of another gene in the phenotype

Question 12

Define evolution

Answer 12

Change in allele frequencies (in a population) over time

Question 13

Define gene

Answer 13

> Sequence of bases on DNA molecule located on chromosomes

>Instruct protein synthesis

Question 14

Define genotype

Answer 14

The genetic constitution of an organism i.e. the alleles an organism has

Question 15

Define homologous chromosome

Answer 15

> Capable of doing meiosis

>Similar/same sequence of genes/loci

Question 16

Define interspecific competition

Answer 16

Competition between organisms of different species

Question 17

Define intraspecific competition

Answer 17

Competition between organisms of the same species

Question 18

Define locus

Answer 18

Fixed position of a gene on a chromosome

Question 19

Define multiple alleles

Answer 19

When a gene has more than two alleles

Question 20

Define phenotype

Answer 20

The expression of the genetic constitution and its interaction with the environment i.e. an organism’s characteristics

Question 21

Define population

Answer 21

All the organisms of one species in a particular habitat (at the same time)

Question 22

Define sex-linked

Answer 22

Gene with loci a sex chromosome (X or Y)

Question 23

Define succession

Answer 23

Process by which an ecosystem changes over time

Question 24

Describe and explain the process of primary succession

Answer 24

> Pioneer species
Adapted to hostile abiotic conditions colonise environment
Make conditions less hostile
New species outcompetes pioneer species -> may change environment to be less suitable for previous species
Becomes dominant species, until outcompeted
Biodiversity, and therefore complexity + stability, of ecosystem increases
Until climx community, the final stage, is reached

Question 25

Describe directional selection

Answer 25

> Selection in favour of individuals with a single, extreme phenotype
Occurs in response to an environmental change

Question 26

Describe disruptive selection

Answer 26

> Selection in favour of individuals with extreme phenotypes, opposing stabilising selection
Occurs whes when environment favours more than one phenotype

Question 27

Describe how abiotic factors can affect population size

Answer 27

> Ideal conditions allow for fast growth and successful reproduction
Otherwise, energy expended on body processes compensating for non-ideal conditions
Example: environment above / below mammal’s body temperature => more energy expended on maintaining core temperature

Question 28

Describe how natural selection arises

Answer 28

> Variation in individuals of the same species
Selection pressures -> predation, disease, competition
Result in differential survival and reproductive success

Question 29

Describe how quadrats placed along a belt transect can be used for estimating the size of population

Answer 29

> Lay measuring tape along length of area being measured
Place quadrats all along the tape (belt transect)
Or at regular intervals (interrupted belt transect)
Record percentage cover or abundance of species within each quadrat

Question 30

Describe how randomly placed quadrats can be used for estimating the size of population

Answer 30

> Frame quadrats placed on the ground at different, randomly generated co-ordinates
Percentage cover of each species present calculated
A square is counted if species covers > 50% of square