What is speciation?
The formation of new species.
What is a species?
A group of organisms capable of interbreeding to produce viable, fertile offsprings.
What is required for a species to evolve into two different species?
- Reproductive isolation of the two populations (cut off gene flow)
- Genetic divergence (genes must change (mutations, chromosonal abnormalities)
What are the 2 major kinds of reproductive isolation mechanism?
Pre-zygotic isolating mechanisms: When something prevent gamete fusion. (formation of a zygote)
Post-zygotic isolating mechanisms: When mating between individuals occurs, but the hybrid is never able to pass off its genes.
What is a hybrid?
The offspring of a mating between individuals of two different species.
What are some kinds of pre-zygotic isolating mechanisms? (5)
- Ecological isolation
- Behavioural isolation
- Temporal isolation
- Mechanical isolation
- Gametic incompatibility
What is ecological isolation?
When individuals don’t mate because
they don’t live in the same habitat.
not same habitat
ex: fig wasps
What is behavioural isolation?
Individuals don’t mate because
one sex does not courtship the correct courtship ritual.
differerent courtship rituals
differences in behavior prevent mating between related animal species
What is temporal isolation?
Individuals don’t mate because
they don’t mate at the same time.
don’t mate at the same time
What is mechanical isolation?
Individuals don’t mate because
the sexual organs are not compatible.
incompatible sexual organs
What is gametic incompatibility?
A
When the sperm of one species can’t fertilize the egg of the other species.
sperm can’t fertilize egg
What are some kinds of post-zygotic isolating mechanism? (2)
- Zygotic mortality and Hybrid inviability
- Hybrid infertility
What is Zygote mortality and Hybrid inviability?
When the zygote (or hybrid) cannot survive due to gene combinations that are harmful to its health
X survive -> harmful gene combinations
What is Hybrid infertility?
When the hybrid species is healthy but cannot reproduce to pass its genes to the next generation
hybrid healty but X reproduce
What are two types of speciation? And how its type is determined?
- Allopatric speciation
- Sympatric speciation
Depends on wether geographic barriers are responsible for the reproductive isolation or not.
What is allopatric speciation?
When 2 pop. are geographically separted.
or
When a physical barrier interrups gene flow between populations.
Ex: formation of an ocean -> 2 tectonic plates moved
What is sympatric speciation?
And how is it possible?
When new species arise even though the two pop. share the same geographical location.
a) From ecological isolation
b) From polyploidy (plants only)
How can sympatric speciation happen because of ecological isolation?
They don’t live in the same habitat.
(still no physical barrier)
ASK TEACHER
How can sympatric speciation happen because of polyploidy?
When gametes have the wrong nb. of chromosomes because of errors during meiosis. (3 or + chromosomes of each types)
->
What are some patterns of speciation? (2)
And what are they?
- Descent with modification: adaptation to a changing envir. slowly produced new species over time.
- Adaptive radiation: new species moves to new ecosystem with many diff. habitats to adapt to and many new species form in a short period of time.
- comme un éventail ou rateau.
1. lots of speciation events
What are two kinds of extinction?
- Background extinction: normal rate of species extinction due to evolution by natural selection.
- Mass extinction: when the species extinction rate -> way higher than background extinction rate over a short period of time.
What are 2 human activities that cause loss of biodiversity? What are they?
- Habitat destruction: loss of necessary elements of the ecological niche of species -> they can’t survive.
- Biomagnification: concentration of non-biodegradable toxic chemical -> it increases as it moves up the food chain -> effect on higher-level predators.
