speciation Flashcards
learn about speciation
species
A group of organism that normally interbreed in nature to produce fertile offspring
speciation
The formation of one or more a new species results from a group becoming reproductively isolated and gene flow no longer exists
cline
species that show a gradual change in phenotype over a geographical area
deme
a local population that has little or no gene flow with members of other populations
bottle neck effect
when a large population is reduced to large numbers, the result of a catastrophic environmental event
founder effect
when a small group of individuals move away and become isolated from the original population
genetic drift
change in allele frequency due to chance rather than natural selection
ring species
a special type of cline which has a circular or looped geographical distribution
stabilizing selection
extreme phenotypes are chosen against and the average phenotype is favoured
directional selection
a single phenotype is selected for and the allele frequency shifts in one direction
disruptive selection
individuals at both extremes of the distribution are selected for whereas the average phenotype is selected against
selection pressures
are factors that affect fitness / reproductive success and include limits on resources (food, habitat, space, and mates) and the existence of threats (predators, disease, climate change)
Reproductive isolating mechanisms
a mechanism or a factor which prevents successful reproduction between 2 species (prevents gene flow between 2 gene pools)
Pre-zygotic RIM
prevents successful reproduction between two species before fertilization
Post-zygotic RIM
prevents successful reproduction between 2 species after fertilization
Geographical isolation
results from physical barriers (ed rivers, mountains, oceans) separating populations
Temporal isolation
Activity, mating, breeding seasons or flowering occur at different times of the day, month or year
Ethological/ behavioural isolation
differences in behaviour, courtship rituals, calls or colouration
Ecological isolation
occupy and exploit different habitats in the same geographical area so that populations rarely come into contact with each other (different herbivore insects feed and mate of different species of plant)
Structural (morphological) isolation
difference in the structure of the external reproductive sexual organs do not allow for sperm transfer
Gamete incompatibility isolation
gametes are incompatible and are unable to fuse and produce a viable zygote
Allopatric species
(closely) related species that live in different geographic locations
Sympatric species
(closely) related species that live in the same geographic location
Hybrid inviability
embryo or offspring is inviable (unable to survive or develop normally) so dies early in its development
Hybrid sterility
hybrid reaches maturity but is infertile so cannot breed
Hybrid breakdown
hybrid reaches maturity and is able to breed but the next generations are infertile or have reduced reproductive capactiy
polyploidy
results when cells contain three or more copies of each chromosome. a result of non-dis junction during meiosis
Autopolyploidy
involves the multiplication of the entire genome within a single species
Allopolyploidy
where two different species produce an infertile hybrid
Allopolyploidy
where two different species produce an infertile hybrid
Advantage of polyploids
- larger cells = larger, more resistant plants with better characteristics (bigger seeds or larger flowers)
- polyploidy with uneven numbers of chromosomes are sterile so any resulting fruit will have no seeds
- greater advantages to grow in various habitats and contain a range of adaptations from both species
Advantage of polyploids
- larger cells = larger, more resistant plants with better characteristics (bigger seeds or larger flowers)
- polyploidy with uneven numbers of chromosomes are sterile so any resulting fruit will have no seeds
- greater advantages to grow in various habitats and contain a range of adaptations from both species
Analogous structures
unrelated species have structures or traits that have a similar function but do not have a common ancestor
Homologous structures
species with a common ancestor have the same basic structure but have adapted to use it for different purposes
Vestigial structures
an organ, tissue or bone that is function-less in an organism but were used by the species ancestor
Divergent evolution
when two or more related groups evolve into new species because they occupy different niches
Coevolution
reciprocal evolutionary change in which a change in a feature of one species acts as a selection pressure for a change in a feature of an unrelated species
Adaptive radiation
a type of divergent evolution which involves the rapid evolution of a large number of species
Convergent evolution
when unrelated species occupy similar niches and evolve similar adaptations (subject to similar selection pressures)
Molecular clock
using rates of mutations in mitochondrial DNA to provide evidence in evolutionary patterns
Parallel evolution
similar features evolve in related or unrelated species because both have been subjected to similar selection pressures
Parallel evolution
similar features evolve in related or unrelated species because both have been subjected to similar selection pressures
Five fingers of evolution
little finger-small population (founders or bottleneck effect)
Ring finger- mating selection
middle finger- mutation
pointing finger- movement (emigration and immigration)
Thumb- natural selection
micro evolution
small change in a species
macro evolution
a large change that can lead to speciation
evolution
a change in the gene pool of a population over time
Mutation
a permanent change in the base sequence of DNA which leads to new alleles
gene pool
the total set of alleles that are present within a population
Allele frequency
the number of times a gene shows up in a population
Migration
a set, mass movement of a species to another predetermined location
immigration
moving into a population
emigration
leaving a population
