Speciation Flashcards
How do we generally define species?
group similar things together,
What are some problems with defining species?
we need to identify species in a way that reflects evolutionary history, variety of different definitions
What are the different species concepts?
morphological, ecological, phylogenetic, and biological
How does the morphological species concept define species?
using similar physical (morphological) features, look similar to members of the species and different from others,
Why do some biologists disagree with the morphological species concept?
sometimes members of the same species look different (humans), convergent evolution can be misleading, the weight of characters or traits
How does the biological species concept define species?
members of the same species can interbreed with one another and produce viable offspring (healthy and fertile)
What is the most commonly used species concept among biologists?
biological
When is the biological species concept not applicable?
extinct species, asexual organisms, organisms with alternative modes of reproduction, hybrids
How does the ecological species concept define species?
a species is a group of organisms that are all adapted to a particular type of resources, called a niche
because selection favours certain phenotypes in a niche
What is the challenge in the ecological species concept?
identifying the niche
How does the phylogenetic species concept define species?
estimate the phylogeny of populations and then identifies the smaller monophyletic groups (most similar DNA)
species have a shared and unique evolutionary history
What is an advantage and a challenge for the phylogenetic species concept?
can be applied to any type of organism
because slight differences are found among every group of organisms it can divide them up into to many groups
What are some reproductive isolating barriers?
pre-zygotic (makes mating hard) and post-zygotic (zygote doesn’t survive)
What are some pre-zygotic isolating mechanisms?
ecological isolation, temporal isolation, behavioural isolation, mechanical isolation, gametic isolation
What is ecological isolation?
when two species have different habitats and don’t interact and therefore can’t mate
What is temporal isolation?
when two species that live in the same ecological range have different times when they sexually mature/breeding seasons
What is behavioural isolation?
different species don’t mate because they have different mating calls, chemical cues, sexual displays, etc
What is mechanical isolation?
when two species have a physical difference that makes it hard to mate (size, incorrect flower shape for pollination)
What is gametic isolation?
when the sperm and egg of different species have incompatible plasma membrane receptors and cannot make a zygote
What are some post-zygotic isolating mechanisms?
hybrid inviability, hybrid sterility, hybrid breakdown
What is hybrid inviability?
mating between two individuals creates a hybrid that does not survive past the embryonic stages
What is hybrid sterility?
species are closely related enough to produce viable hybrids, but the hybrids are sterile (infertile)
What is hybrid breakdown?
two species can make a hybrid that is viable and fertile, but the successive generations decrease in viability and fertility
What is speciation?
when a new species is created
What is allopatric speciation?
when a new species is created through geographic isolation
What is sympatric speciation?
when a new species develops in the same geographic area
If a flood seperates two populations, what process would this be?
allopatric speciation
Dog breeders isolate the different dog breeds when they are fertile, what isolation is this the most similar to?
ecological isolation
What is the most likely order of events in allopatric speciation?
genetic isolation then genetic drift then divergence
If two lizard species don’t mate because of differing mating rituals what type of isolation is occuring?
behavioural isolation
A mule is an example of what posyzyogtic barrier?
hybrid sterility
Local variants of species that interbreed where their distributions overlap are called what?
subspecies
When does vicariance occur?
when a population is fragmented into isolated subpopulations
How can sympatric speciation occur?
instantaneously through formation of polyploid offspring, disruptive selection
What can result in allopatric speciation?
dispersal and vicariance
What are some pathways that lead to polyploidy?
autopolyploidy and allopolyploidy
What is autopolyploidy?
when an individual has a complete extra set of chromosomes that is derived from a single parental species (usually by self-fertilization)
What is allopolyploidy?
occurs when an individual has multiple sets of chromosome sets derived from different species
Why do plants speciate from polyploidy more than animals?
the reproductive cells in plants are not seperated early in development, some can self-fertilize, hybridization is more common
What is a hybrid zone?
An area where two populations may breed and produce viable, fertile offspring
