3.5 Evolutionary processes leading to speciation

Question 1

divergent evolution/ divergence

Answer 1

an evolutionary pattern where two related but isolated populations accumulate genetic differences and become more and more different due to each population being subjected to different selection pressures.

Question 2

adaptive radiation

Answer 2

The rapid evolution of a large number of species from a common ancestor, to occupy a variety of different ecological niches (vacant niches)

Question 3

convergent evolution

Answer 3

an evolutionary pattern in which 2 or more unrelated species (no common ancestor) evolve similar adaptations in response to similar niche requirements and similar selection pressures.

Question 4

co-evolution

Answer 4

an evolutionary pattern that describes the reciprocal evolutionary effect that two interacting species can have on each other. Each species acts as a natural selective influence on the other

Question 5

gradualism

Answer 5

A slow, constant rate of change within a species occurring over time which involves the transition of one species into another, in response to changes in selection pressures.

Question 6

punctuated equilibrium

Answer 6

An evolutionary pattern characterised by long periods of little change (stasis), followed by a rapid burst of evolutionary change with the sudden appearance of new species

Question 7

stasis

Answer 7

long periods of time with little to no evolutionary change

Question 8

homologous structures

Answer 8

adaptations/structures that are similar in structure and origin, but are different in function

Question 9

analogous structures

Answer 9

structures present in different unrelated species (no common ancestry) that have the SAME FUNCTION, due to similar selection pressures.

Question 10

vestigial structures/ organs

Answer 10

structures that have been reduced and/or lost their function, but the remnant of the structure shared with the common ancestor/ closely related species is still present

Question 11

selection pressure

Answer 11

Selection pressures are external factors which affect an organism’s ability to survive in an environment (the effects of natural selection on the population). Individuals with favourable phenotypes/ better suited to the environment will have a greater chance of survival and reproduction.

Question 12

parallel evolution

Answer 12

a pattern of evolution where two or more related groups evolve along similar lines independently

Question 13

mutation

Answer 13

A random, spontaneous, permanent change in the nitrogen base sequence, which gives rise to new alleles

Question 14

common ancestor

Answer 14

An ancestor that two or more descendants have in common.

Question 15

speciation

Answer 15

A process that involves the formation of new species as a result of populations becoming reproductively isolated; therefore no longer sharing a common gene pool.

Question 16

anagenesis

Answer 16

formation of a new species where no splitting is occurring (the new species replaces the old species and so no members of the old species exist anymore)

Question 17

phylogeny

Answer 17

the study of evolutionary relationships

Question 18

phylogenetic tree

Answer 18

Diagrams that show the evolutionary relationships between different groups (taxa)

Question 19

pentadactyl limb

Answer 19

A limb with five digits (e.g. hand), characteristic of tetrapod vertebrates (amphibians, reptiles, birds, and mammals). It evolved from the paired fins of primitive fish as an adaptation to locomotion on land and is not found in modern fish.

Question 20

prezygotic isolating mechanism

Answer 20

mechanisms that act prior to fertilisation; includes structural/ behavioural/ geographical/ temporal/ ecological barriers

Question 21

postzygotic isolating mechanism

Answer 21

mechanisms that act after fertilisation; includes hybrid inviability/ hybrid sterility/ hybrid breakdown

Question 22

Geographic isolation

Answer 22

RIM caused by physical barriers, such as rivers, mountain ranges, and oceans separating populations.

Question 23

Structural isolation

Answer 23

RIM caused by the evolution of differences in structure of the external sex organs (genitalia), so that the male is no longer able to successfully transfer sperm to the female.

Question 24

Ecological isolation

Answer 24

RIM caused by differences in habitat/ niches within the same geographical area, so that populations have greatly reduced contact with each other.

Question 25

Temporal isolation

Answer 25

RIM caused by species’ breeding behaviours occurring at different times.

Question 26

Behavioural isolation

Answer 26

RIM where, within one geographical area, variations in the courtship displays/ behaviours (e.g. songs) of different individuals of the same species developed.

Question 27

Gametic isolation

Answer 27

RIM caused by the evolution of incompatible gametes.

Question 28

Hybrid inviability

Answer 28

When the embryo is inviable- i.e. doesn’t survive/ develop normally, therefore dies early in development.

Question 29

Hybrid sterility

Answer 29

When the hybrid survives to reach maturity, but is infertile, and therefore can’t reproduce sexually

Question 30

Hybrid breakdown

Answer 30

mechanism/ process which involves the hybrid surviving to reach maturity and being fertile, yet the next/ subsequent generations are infertile/ have reduced fertility.

Question 31

polyploidy

Answer 31

A form of sympatric speciation that involves the formation of organisms with multiple sets of chromosomes in their somatic cells. Results in the formation of a new species without isolation from the parent species.

Question 32

auto polyploidy

Answer 32

A from of polyploidy where the polyploid organism was produced by organisms of the same species.

Question 33

allopatric speciation

Answer 33

The formation of new species from an ancestral species, due to geographical isolation (caused by geographical barriers).

Question 34

sympatric speciation

Answer 34

The formation of new species from an ancestral species while both inhabit the same geographic area.

Question 35

reproductive isolating mechanisms

Answer 35

factors that prevent interbreeding between groups of individuals which leads to speciation.

Question 36

ring species

Answer 36

A special type of cline that forms a loop because the two ends of the cline overlap. The two ends of the cline are connected by a series of intermediate, interbreeding populations.

Question 37

ring species

Answer 37

A special type of cline that forms a loop because the two ends of the cline overlap. The two ends of the cline are connected by a series of intermediate, interbreeding populations.

Question 38

comparative anatomy

Answer 38

The comparison of body structure between different species, both from the fossil record and those living.

Question 39

comparative anatomy

Answer 39

The comparison of body structure between different species, both from the fossil record and those living.

Question 40

species

Answer 40

Organisms that can interbreed and produce viable (fertile) offspring.

Question 41

species

Answer 41

Organisms that can interbreed and produce viable (fertile) offspring.

Question 42

subspecies

Answer 42

populations of a species that are different to each other in one more characteristics, but can still breed with each other.

Question 43

deme

Answer 43

Local interbreeding (with existing gene flow) populations that may be geographically separated.