species and speciation Flashcards
(23 cards)
what is a species
morphological species concept- relies on the similarities within species and differences within species. most common way but not most accepted. things are measured baed on wha you know about those individuals.
why is difficult to distinguish species
specification is an attempt to create classifications. it cannot capture the complexity of it.
what are the pros of morphological/taxonomical species concept
easy to measure characteristics and can use fossils or museum species
what are the cons of the morphological species concept
differences can be due to environment (two specimens may be the same like changes in colour may not actually be a telling factor) eg. hydrangeas and many miss cryptic species (they can look the same but are actually different)
what is species
composed of interbreeding populations and subject to evolutionary forces - meaning that you’re swapping genes and your subject to natural selection as a group
what is the biological species concept
-actually or potentially interbreeding natural populations- interbred and produce fertile offspring
-reproductively isolated from other such groups (have they met or not)
- widely accepted and form the basis of biodiversity laws
what are the mechanisms that keep species separate (pre zygotic)
prezyogitc isolation mechanisms: before an embryo is formed
1. temporal: mating changes in time - so two potential interbreeding populations never do
2. ecological: they live in different habitat - one in trees and one in land
3. behavioural: different courtship behaviours
4. mechanical: can’t physically breed together because sexual interaction is not possible
what are the mechanisms that keep species separate (post zygotic)
hybrid inviability-create a living hybrid but die before reaching adulthood
hybrid infertility- forms a hybrid but infertile
hybrid breakdown-offspring per generations becomes worse and worse
why is hybridisation an issue
its common and are fertile. they have lower fitness than parent species. eg. coy wolves are not put in species according to biological species concept
in terms of biological species concept, how is hybridisation concept fit in
they are not able to hybridise or can but it dies or have very low fitness
what are ring species
distinct species but can mate with random other and some not
what are the pros or mophological species concept
- makes intuitive sense
- makes sense
- may reveal cryptic species that are similar ut can’t interbreed
- widely accepted
what are the cons of mophological species concept
- species that can form hybrids are not considered
- difficult to test in many cases
- only applies to sexual organisms
phylogenetic species concept
- smallest set of organisms that share an ancestor and can be distinugihed from other such sets- can be morphological or genetic
what are the pros of phylogenetic species concept
- can deal with aseuxal organisms
- detect cryptic species
- includes ideas from biological and morphological concept
what are the cons of phylogenetic species concept
- genetic analysis still expensive
- requires specialist equipment
- requires individuals from related species
how do species form
anagenesis and cladogenesis
what is anagenesis
one specie over time under selection morphs into another. there is limited evidence.
what is cladogenesis
single ancestor split into two species
what are the possible modes of speciation
allopatric: no gene flow.
parapatric: some gene flow
sympatric: major gene flow
when does allopatric form
a barrier forms between a population causing them to evolve separately. eg. mountain forms
what does parapatric mean
original population forms along some environemntal gradient and two species from either end adapt to their environment and evolve. you get two distinct and a hybrid in the middle eg. wet and dry zone.
what does sympatric mean
original population and within the same population there is different smth hat leads to different species that occur in the same area. eg. flys going to hawthorn and some going t apples- they need to lay their eggs where they are born so theres difference in species with those who live in hawthorns and apples.
