3.7.3 Evolution may lead to speciation Flashcards Preview

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Flashcards in 3.7.3 Evolution may lead to speciation Deck (55)
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1

What do you call the environmental factors that limit the population of a species?

selection pressures e.g. predation, disease, competition

2

Define gene pool

All of the alleles of all of the genes of all the individuals within a particular population at a given time

3

All populations have the potential to increase exponentially - why in nature is this rarely the case

death rates must be high which is compensated for by the high reproductive rates. Some species have lower reproductive rates but have higher degree of parental care , the lower death rate from this maintains their population size.`

4

What is the consequence of over-production?

competition between individuals - intraspecific

5

What determines which individuals survive in over production?

The best adapted organisms to the conditions at the time survive and reproduce and pass on favourable allele combinations.

6

Why do organisms NOT produce organisms identical to itself when it survives the condition it lives in?

Meiosis - offspring produce show variation from the parent, this may may result in offspring more or less likely to survive. Environment changes all the time, this way there is an wide range of genetically different organisms in the population.

7

Consequences of populations showing little genetic diversity

more vulnerable to disease and climate changes.

8

A larger population showing greater genetic diversity means

There is a greater chance that one or more individuals will have the correct combination of alleles for survival

9

Individuals that survive the struggle for survival can

more likely to breed/reproduce, pass on favourable allele combinations to future generations.

10

Name 3 types of selection

stabilising, directional and disruptive

11

Describe stabilising

preserves the average phenotype, selection against extreme phenotypes. Environment pretty stable

12

Describe directional

Phenotype of population changes, favouring phenotype at one direction from the mean (selection for one extreme phenotype). Environmental conditions change.

13

Describe disruptive

Preserves individuals with extreme phenotypes (both ends), not those around the mean. Opposite to stabilising. Least common selection. Environment changes taking 2 distinct forms

14

which types of selection is being described: A baby born with a birth weight of more than 4kg and less than 2.5kg has a greater risk of dying

stabilising

15

Elephants have evolved longer trunks enabling them to reach leaves higher up in the trees

directional

16

small mammals can escape from predators by hiding in small places while large mammals can resist attack from predators

disruptive

17

the most important selection in bringing about evolutionary change

disruptive

18

define speciation

the evolution of a new species from an existing one

19

define a species

group of similar organisms that are capable of breeding and producing fertile offspring - they share a common ancestry (same genes different alleles)

20

summarise how a new species is formed

because of reproductive separation, variation followed by natural selection

21

define adaptive radiation and consequences of this

when each population becomes adapted to its local environment, leading to changes in allele frequency in the population

22

identify 2 forms of speciation

allopatric and sympatric

23

the genetic diversity of a small population can be described as

Less - as there is a smaller variety of alleles in a small populations

24

the genetic diversity of a large population can be described as

Great - as there is a larger variety of alleles in a large populations

25

The effect of genetic drift is greater on which population size - small or large?

small

26

Allopatric means

different countries

27

Allopatric speciation means

When 2 populations become geographically isolated

28

Examples of geographical isolation...

physical barrier which prevents interbreeding e.g. oceans, rivers, mountains, deserts.

29

Define reproductive separation

when 2 populations can no longer interbreed and produce fertile offspring

30

Example of allopatric speciation

Finches on the Galapagos Islands!