Speciation - EXAM Memorisation

Speciation

formation of a new species

RIM

mechanism/process that prevents individuals in a population/different species from interbreeding and producing fertile offspring

Species

individuals that interbreed to produce fertile offspring

What do isolating mechanisms do

reduce gene flow between two groups

Ecological Isolation

pre-zygotic RIM in which two (closely related) populations live in the same geographic region but occupy different habitats/ecological niches, so they don’t mate

Temporal Isolation

different development times, different breeding seasons, therefore the opportunity to interbreed is reduced

Behavioural Isolation

Pre-zygotic RIM where difference in courtship rituals, mating calls, or specific behavioural signals prevent members of different species from interbreeding, even when they might live in the same area

Structural RIMs

pre-zygotic RIM that prevents different species from mating and fertilising eggs due to physical or anatomical incompatibilties

Gamete Mortality RIM

Pre-zygotic RIM in which sperm or egg cells from different species meet, but the gametes themselves fail to survive long enough to achieve fertilisation

Hybrid Inviabiltiy

Post-zygotic RIM in which the hybrid formed by the mating of 2 different species fail to (egg) develop properly or survive to reproductive age

Hybrid Sterility

Post-zygotic RIM in which the hybrid formed by 2 different species is unable to reproduce

Hybrid Breakdown

Post-zygotic RIM in which the first generation hybrid formed by the mating of 2 different species are viable/sterile but the subsequent generations are sterile or inviable

Convergent Evolution

species/organisms that are not closely related independently develop/evolve similar appearances/physical features in response to living in an environment which has similar selection pressures

Ananlgous Structure

similar morphology/feature/body part that has a similar function in unrelated species/organisms

Divergent Evolution

two or more species share a common ancestor but evolve different traits over time due to different selection pressure

Selection Pressure

any environmental factor (abiotic/biotic) that affects an organism’s ability to survive and reproduce

Relation between convergent and analogus structure

convergent evolution causes analogous structure

Comparative Anatomy (explain)

Compare analogous and homologous structure to determine if similarities resulted from a shared ancestor or evolved independently. If species have similar physical features that can be linked back to a common ancestor, would indicate divergent evolution. If species have similar features that cannot be linked back to a common ancestor, would indicate convergent evolution

Molecular biology (explain)

Compare DNA/proteins/mtDNA. If species have a higher DNA sequence/protein match, they are likely to have divergence from a common ancestor. If species look alike but have dfferent DNA sequences/proteins, their similarities are likely to come from similar selection pressures/convergent evolution

Fossil Record (Explain)

analyse evolution changes. Fossils showing changes in structural adaptations over time from a common ancestor may indicate divergent evolution, whereas fossils that that show the same trait in multiple, distantly related species indicate convergent evolution

Biogeography (Explain)

analyse where species live and can determine if traits came about a common ancestor or came independently. Species that have a common ancestor but live in different environments and evolve different adaptations would indicate divergent evolution. Species with similar traits found in different locations but with similar environments would indicate convergent evolution.

Hybrid

two different species (or genetically different populations) interbreed

Polyploidy ?????

a cell or organism has 3 or more times the set chromosome number. This occurs when there is an error during meiosis. Chromosomes fail to seperate during meiosis, producing diploid gametes rather than haploid gametes

Allopatric speciation

A population is seperated by a geographic barrier and gene flow is prevented. Over time, processes such as mutation/genetic drift/natural selection cause the two populations to become seperate species.

Sympatric Speciation

Speciation occurs in the same geographical area. It is caused by isolating mechanisms such as temporal/behavioural/ecological/structural/polyploidy.

Polyploidy as a server of speciation

hybrids are an instant species as they could not reproduce with either parent species due to difference in chromosome number. Gene flow cannot occur due to gamete incompatibiltiy

Punctuated Equilibrium

rapid evolutionary change in short periods followed by periods of stabiity.

Gradualism

slow, continous change, with small changes accumulating over millions of years

Founder Population

a small subset of a population breaks away from the main population (Colonises a new area)

Gene flow

movement of alleles between populations

Founder Population & Alleles

founder population will not have the full range of alleles as the main population, which may lead to differences between them increasing over time

Tectonic events

lead to species being geographically seperated

Adaptive Radiation

multiple species evolving from a single ancestor species

Why does adaptive radiation occur

due to open niche

What is required for adaptive radiation/speciation

a lot of time, less for adaptive radiation as compared to speciation

Selection Pressure

environmental factors that influence the likely success of an individual

Natural Selection

individuals with the most favourable phenotype/adaptations/traits to the environment will survive and reproduce, and will pass on these favourable alleles on to their offspring

Mutation

random permanent change in the DNA base sequence

Gene Pool

all the alleles contained in a population

Genetic Drift

random change in the allele frequency of a population

Where is genetic drift more prominent

smaller populations which tend to arise from founder effect or bottleneck effect

Consequences of genetic drift

alleles becoming fixed or lost, loss of genetic diversity/smaller gene pool

Mutation and natural selection

harmful mutations are selected out of the population, allowing small populations to survive despite limited genetic diversity,

niche

role of the organism within its environment

Coevolution

Over time, two unrelated species develop specific adaptations to enable their existence in the presence of other organism

Endemic Species

organisms found in one location and no where else

Evolution

change in the heritable traits of a population over successive generations

Macroevolution

evolutionary processes and patterns which occur at and above the species level

Microevolution

change in allele frequencies that occur over time within a population

Common ancestor

ancestral organism shared by 2 or more descendent lineages

Subspecies

smaller groups within a species that are still capable of breeding with each other despite minor anatomical or genetic difference

Directional selection

type of natural selection that favours one extreme phenotype over the average and the other extreme

Disruptive Selection

type of natural selection that favours individuals at both extremes of a trait over individuals with the intermediate phenotype

Stabilising selection

favours individuals with the intermediate phenotype over individuals with either extremes of a trait

Bottleneck effect

population rapidly decreases in size due to natural disaster, human hunting, leading to alles becoming lost or fixed

Abiotic Factors

non-living part of an ecosystem that influence the survival of an organism

Biotic Factors

living organism that influences the surivival of another organism and shape its ecosystem

Parallel evolution

evolution of similar features, not present in ancestral form, in 2 or more closely related species

Gametic Isolation

Pre-zygotic RIM in which the sperm and egg meet but fail to fuse and form a zygote

Geographical isolation

Pre-zygotic RIM in which a physical barrier prevents gene flow between populations

Post-zyogtic RIM

Reproductive isolating mechaisms that take place after fertilisation to prevent successful interbreeding

Seual Selection

members of one sex chose a member of the opposite sex to mate with, individuals with certain traits are more likely than others to obtain mates and reproduce

Homologous structure

physical features found in different organisms that share a common ancestor

fossil

any preserved remnant of an organism from a past geologic age found in the earth’s crust

Evolution & Contribution to Speciation

Provides the fundamental mechanisms by which

gene pools diverge over time until populations can no longer

interbreed.

Macroevolution & Contribution to Speciation

provides the cumulative genetic changes, environmental pressures, and evolutionary mechanisms that cause populations to diverge until they can no longer interbreed

Microevolution & Contribution to Speciation

continually introduces and alters genetic traits in a population

Speciation & Contribution to Speciation

creates distinct, independent gene pools and evolutionary lineages

Mutations & Contribution to Speciation

introduce unique genetic variations into isolated populations that can be acted upon by natural selection or genetic drift which eventually prevents gene flow and splits a single lineage into 2 distinct species

Gene flow & Contribution to Speciation

speciation begins once a barrier stops gene flow between 2 groups. Independent mutations, natural selection, and genetic drift begin to accumulate in each population until the two populations can no longer interbreed

Natural Selection & Contribution to Speciation

causes populations of the same species to adapt to different environments or ecological niches, eventually leading to reproductive isolation

Directional Selection & Contribution to Speciation

causes populations phenotypes to shift away from ancestral forms in response to changing environments, aiding divergence

Disruptive Selection & Contribution to Speciation

contributes to speciation by simultaneously favouring individuals at both extreme ends of a trait spectrum while selecting against individuals with intermediate traits. If population splits into 2 distinct phenotypic group within the same area, sympatric speciation occurs

Stabilising Selection & Contribution to Speciation

acts to maintain the status quo of a species by favouring intermediate phenotypes and selecting against extreme variations at both ends of a trait spectrum. Consequently, it decreases genetic diversity and keeps the population’s trait distribution stable around an optimal mean

Selection Pressure & Contribution to Speciation

causes seperated or distinct sub-populations to diverge genetically over time until they can no longer interbreed

Genetic Drift & Contribution to Speciation

causes unpredictable divergence in allele frequencies, particularly in small populations, accelerating reproductive isolation

Bottleneck Effect & Contribution to Speciation

alters allele frequencies rapidly and randomly, leaving the surviving population genetically distinct from the original population

Founder Effect & Contribution to Speciation

establishes a new genetically distinct population that can rapidly diverge from the ancestral source via natural selection and genetic drift

Abiotic Factors & Contribution to Speciation

create physical environmental gradients and selection pressures that favour specific adaptive traits in distinct niches

Biotic Factors & Contribution to Speciation

exert selective pressures that drive biological divergence

Divergent Evolution & Contribution to Speciation

common ancestral traits adapt along different evolutionary pathways until distinct species are formed

Convergent Evolution & Contribution to Speciation

does not produce speciation but demonstrates how similar environmental selection pressures act on distinct lineages

Co-evolution & Contribution to Speciation

drives specialised adaptations that can lead to reproductive isolation and speciation

Parallel Evolution & Contribution to Speciation

actively drives speciation - specifically ecological speciation - by establishing reproductive barriers through parallel adaptations

Punctuated Equilibrium & Contribution to Speciation

when environmental conditions shift dramatically or a small group becomes isolated after a long period of stability, genetic drift and strong local selection pressures cause rapid evolutionary changes, creating new species

Gradualism & Contribution to Speciation

over thousands to millions of generations, the small point mutations gene duplicants and subtle chromosomal rearrangements, which occur continuously in a population, add up, gradually pushing a population’s physical and behavioural traits away from those of its ancestor

Adaptive Radiation & Contribution to Speciation

causes a single ancestral species to rapidly diverse into multiple new species, each adapted to fill distinct ecological niches

Allopatric Speciation & Contribution to Speciation

physical geographical barriers allow natural selection and genetic drift to establish reproductive isolating mechanisms

Sympatric Speciation & Contribution to Speciation

causes the divergence of a single ancestral species into two or more distinct species without any physical or geographical isolation

Polyploidy & Contribution to Speciation

causes instantenous reproductive isolation and generating new genetic traits

Autopolyploidy & Contribution to Speciation

causes instantaneous, single-generation

reproductive isolation within a single ancestral population

without requiring hybridization between different species.

Allopolyploidy & Contribution to Speciation

- combines interspecific hybridization

(hybridization between different species) with chromosome

doubling, producing a completely new, fertile, and

reproductively isolated species within two generations.

RIMS & Contribution to Speciation

act as biological barriers

that prevent individuals of different populations from

interbreeding or producing fertile offspring( block gene flow).

This allows separated populations to accumulate genetic

differences independently until they become distinct species.

Pre-zygotic RIMS & Contribution to Speciation

prevent gene flow before

fertilisation occurs which allows mutation, genetic drift, and

natural selection to lock in genetic separation permanently and

force populations to evolve along separate evolutionary paths

until they become distinct species.

Temporal Isolation & Contribution to Speciation

prevents gene flow between populations due to

differences in the timing of mating, breeding seasons, or active

hours. This causes their gene pools to remain separate, allowing each population to evolve independently over time.

Ecological Isolation & Contribution to Speciation

populations need to adapt to different

environmental resources or conditions, so rarely encounter one

another during their mating periods, effectively halting gene flow

Behavioural Isolation & Contribution to Speciation

mate choice is driven by distinct

behavioural cues so individuals actively choose mates only from within their own group, effectively halting gene flow even when

populations live in the exact same geographic region.

Structural Isolation & Contribution to Speciation

If two individuals meet and attempt to reproduce, their physical structures are incompatible blocking gene flow between populations.

Gametic Isolation & Contribution to Speciation

Ensures fertilisation fails at the molecular

level even if mating/pollination successfully takes place. This

serves as a definitive barrier to gene flow, forcing diverging

populations to remain genetically independent species.

Geographical Isolation & Contribution to Speciation

initiates allopatric speciation by blocking gene flow and allowing independent mutations, natural selection, and genetic drift to occur