natural selection

Question 1

explain the theory of evolution

Answer 1

living organisms that reproduce sexually show greater variety in appearance

organisms produce excessive offspring (struggle for survival)

organisms that inherit characteristics that give them an advantage pass this down to their offspring

Question 2

define natural selection

Answer 2

process whereby organisms that are best adapted to their environment are most likely to survive and reproduce, passing their advantageous alleles down to their offspring

Question 3

what is a niche?

Answer 3

role an organism plays within the habitat it lives in

Question 4

what are anatomical adaptations?

give example.

Answer 4

adaptation in form/structure of organism

eg thick layer of blubber

Question 5

what are physiological adaptations?

give example.

Answer 5

way body works (biological pathways/enzymes)

eg when driving mammals’ heart rate drops when under the sea

Question 6

what are behavioural adaptations?

give example.

Answer 6

changes to instinctive/programmed behaviour

eg insects/reptiles orientating themselves to get maximum sunlight

Question 7

why do organisms adapt?

Answer 7

so they are able to exploit their own niche so it is different enough to avoid competition

Question 8

define evolution

Answer 8

the process by which organisms develop and change characteristics over a period of time

Question 9

define habitat

Answer 9

the natural environment an organism lives in

Question 10

define adaptation

Answer 10

a change meaning an organism is specialised to suit the environment they live in

Question 11

when does competition happen between species?

Answer 11

when two or more individuals strive to obtain the same resources when they are in short supply

the more similar the individuals are, the more intense the competition

Question 12

suggest reasons for why two species can not occupy the same niche

Answer 12

they have different roles within the community

their adaptations are for specific niches

competing for same resources so one species must outcompete the other

Question 13

explain how moths underwent natural selection

Answer 13

moths that were black stood out so white moths were more likely to survive

industrial - soot and smoke made trees black

black moths had advantageous genes as they blended in better

these survived and reproduce

alleles of population changed

Question 14

define genetic diversity

Answer 14

a measure of all the genes possessedby the individuals in the population

Question 15

define ecosystem diversity

Answer 15

a measure of plant and animal life in the world or in a particular habitat,

Question 16

define species diversity

Answer 16

the number of different species and number of individuals in each species within a specified area

Question 17

explain these three types of selection

-directional

-stabilising

-disruptive

Answer 17

Directional- extreme phenotype favoured over others, allele frequency shifts over time to favour that

Stabilising- favours a non-extreme trait, favours average individuals of population

Disruptive- extreme traits are valued over intermediate ones

Question 18

stages of natural selection

Answer 18

Variation

Intraspecific competition

Those with advantageous alleles are more likely to survive

These reproduce and pass on advantageous alleles

Allele frequency in population changes

Question 19

explain how malpeque disease affected oysters

Answer 19

became small/flabby/pus filled

-small amounts had a certain allele allowing them to be resistant to the disease

-these oysters survived and reproduced

Question 20

explain what speciation is

Answer 20

Two populations become too genetically distinct , evolution of two different species from one existing one.

Reproductively isolated means no mixing of genes can occur

Genetic drift and mutations means they can not reproduce to form fertile offspring (genotype and phenotype become so different overtime, even if reunited, they can not interbreed)

Question 21

explain ALLOPATRIC speciation

Answer 21

Formation of two species from one original , due to geographical isolation

Mountains/rivers/deserts

Question 22

explain SYMPATRIC speciation

Answer 22

Formation of two species from one original due to reproductive isolation, whilst occupying the same niche

Behavioural changes (courtship) , gametic variation, seasonal changes in behaviour

Question 23

isolating mechanisms

Answer 23

geographical (physical barrier)
ecological (species develop preferences to area of habitat)
seasonal (timing of sexual receptiveness)
behavioural (e.g courtship)
mechanical (e.g change in genitalia/stigma)

Question 24

what is adaptive radiation?

Answer 24

adaptive radiation is when one species rapidly evolves to form a number of different species.