bio 3.5

Species

a group of organisms that can successfully interbreed to produce fertile offspring.

Endemic species

species found in one location and nowhere else due to specific niche requirement, strong selection pressures limiting gene flow

Speciation

the formation of a different species from a common ancestral species, gene flow is stopped over time, RIMs are built up in different populations.

Sympatric

living in the one geographical area / different ecological niche or similar.

Sympatric species

closely related species that previously divered from a common ancestor, now exist in the same geographical area at the same time, but remain reproductivly isolated.

Sympatric speciation

the formation of a different species from a common ancestral species in the same geographical area, gene flow is stopped by a non-geographical barrier. (ecological isolation, sexual selection or polyploidy)

Allopatric speciation

the formation of two different species from a common ancestral species when gene flow is stopped by a physical geographic barrier and over time, reproductive isolating mechanisms are built up in the different populations.

Allopatric species

similar species that are geographically separated

Punctuated equilibrium

long periods of stasis followed by rapid periods of change / speciation triggered by sudden changes in environment (changes in selection pressures)

Gradualism

evolutionary process proceed slowly but continuously, so populations of ancestral species slowly diverge from one another.

RIMS

a barrier that prevents tow organisms from different species from mating and producing fertile offspring, preventing sucessful interbreeding and gene flow.

Prezygotic RIM

mechanisms that prevent sucessful fusing of gameetes and therefore the formation of a zygote (GETSG)

Postzygotic RIM

zygote forms but mechanisms prevent its developemt into fertile offspring (HSIB)

Geographical isolation

physical barrer (oceans, mountain ranges) separate population so they cannot come into contact to reproduce, preventing gene flow.

Ecological isolation

individuals of a species live in sameares but differnet ecological niches resulting in them rarely interacting, no reproduction, preventing gene flow.

Temporal isolation

differences in timing of behaviour, preventing mating and gene flow (breed / flower at different times of year, active at dfifernt times of day)

Structural isolation

structural shape of reproductive parts prevents mating, preventing gene flow (genitalia shaped a specific way to prevent hybridisation)

Behavioural isolation

different behaviour and courtship rituals not recognised, prevents mating, preventing gene flow (one species noctural one diurnal)

Gametic isolation

gametes cannot fuse fdue to chemical incompatibility, preventing gene flow (sperm cannot prenetrate egg)

Mutation

the random and permanent change in the base sequence of DNA (only source of new alleles in gene pool)

Gene pool

all the unique inheritable alleles present in a population (gene pool increase when new alleles introduced).

Founder effect

small number of indicvduals leaves larger og population to establish new reproductively isolated somewhere else (small and randwon, genetic diverity decreases)

Bottleneck effect

sudden significant reduction in population size due to catastrophic change event from environment or human activity (tsunami, virus) (small and random, genetic diversity decreases).

Genetic drift

the random change in allele frequency in a population due to random change events. Smaller populations are affected more, alleles easily lost or fixed, each individuals increase count for larger portion of gene pool.

Natural selection

must have variation in phenotypes in a population, process where environmental factors act as selection pressures which select for phenotype best suited to environment, individuals with this favourable phenotype have better survival chances (more fit), so more likely to survive long enough to reproduce and pass on favourable alleles to offspring, the frequency of favourable alleles increases in gene pool over time.

Selection pressure

abiotic / biotic factors that affect biological fitness and reproductive success, limits of resources (food, mates, space) and existence of threats (predators, disease, climate change).

Niche

the role of an organism in its environment, including the abiotic and biotic factors an organic itercats with, their habitat, and their adaptations for survival.

Adaptive radiation

a type of divergent evolution, occurs when a common ancerstal species rapidly evoles into a larger number of new species due to the availability of many new ecological niches with different selection pressure.

Hybrid

an infertile offspring produced by the reproduction of two different species.

Evolution

the change in allele frequencies in a population over time

Allele frequency

the percentage (proportion) of each allele in gene pool

Gene

a section of DNA that codes for a specific trait

Genetic diversity

the diversity of heritable traits in a population (better survival of selection pressures in enviro change)

Gene flow

the movement of alleles between populations / gene pools when individuals migrate between populations.

Stabilising selection

intermediate phenotypes have highset fitness, selection against both extremes.

Directional selection

phenotype towards one end is favoured over other phenotypes, allele frequency shifts in direction of phenotype over time, select against one extreme.

Disruptive selection

two or more phenotypes have higher fitness than intermediate phenotypes, can lead to speciation, selection against mean.

Divergent Evolution

the splittingof a common ancestral species into two or more species that develop different phenotypesdue to becoming specilised to occupy different ecological nieces with different selection pressures.

Convergent Evolution

when two or more distantly related species (no common ancestor) evolve similar features (analogous structures) in response to similar niche requirements and therefore similar selection pressures

Coevolution Evolution

when overtime two unrelated species develop specific adaptations to enable their existence in the presence of eachother. Any change in one species acts as selection pressure causing reciprocal changes in the other species (pollenation + plants).

Homologous structures

structure in different species that are inherited from a common ancestor, similar structure and origin, diff function and selection pressures in different environment.

Analogous structures

structure in different species that are not inherited from a common ancestor, smae function, similar form due to similar environment seleciton pressure.