Unit 3- Speciation Flashcards
What is needed in order to form a new species?
Part of an existing population must become reproductively isolated
Reproductive isolation can come about in 2 different ways:
Allopatric and sympathise speciation
Why do 2 species not form if a species is not reproductively isolated?
If members of 2 groups can still interbreed then there will be gene flow between them so remaining as 1 species
When does allopatric speciation come about?
When 2 populations of the same species become geographically isolated (allopatric meaning different father land)
Give 3 causes of allopatric speciation:
- island drift
- formation of a mountain range
- sea level rises causing body of water barrier
- an impassable rift due to earth quake
- divided by a desert
- divided by a large distance
Describe the stages of allopatric speciation:
1- there is interbreeding amongst a population of species
2- the population becomes divided by a physical barrier, so long as the 2 populations are reproductively isolated there is no gene flow between groups
3- if the environments are different the different characteristics will be selected by natural selection shifting the allele frequencies
4- if the barrier is then later removed the 2 populations are so different that they cannot interbreed to produce fertile offspring
Does speciation occur if the 2 populations are separated by a physical barrier but the environment is identical on both sides?
Yes, the populations will change by random genetic mutations again shifting the allele frequency
What is sympatric speciation?
When 2 populations of the same species become reproductively isolated even though they share the same geographical location (no physical barrier) (sympatric- means same fatherland)
What different ways may 2 species become reproductively isolated?
- geographical isolation
- habitat isolation
- seasonal isolation
- mechanical isolation
- behavioural isolation
- gametic isolation
(Get Horny Soon My Bumholes Gaping)
What is habitat/ecological isolaton?
- when populations become reproductively isolated by developing different niches and occupying different habitats in the same environment, so do not meet to breed
Give an example of habitat isolation
Fruit flies used to only live in and eat hawthorn bushes, A mutant strain of fruit fly arose that had the enzyme to digest apples, so 2 different populations arose living in the different plants occupying a different niche
What is behavioural isolation?
When populations become reproductively isolated by developing different courtship behaviours, as a result not responding to the other populations displays
What is seasonal/temporal isolation?
When 2 populations become reproductively isolated because the timing of their reproductive season changes
What is mechanical isolation?
When populations become reproductively isolated because of a change in their reproductive organ anatomy
What is gametic isolation?
When populations become reproductively isolated because the male and female gametes from2 populations are incompatible together
Certain bacteria are growing resistant to our antibiotics, how can we counter this??
- reduce the use of antibiotics in humans and in food
- use DNA sequencing to identify bacteria finding new ways of targeting them with drugs and genetic engineering
- develops new antibiotics
Summary of speciation:
1- a population becomes separated into 2 reproductively isolated groups
2- the 2 groups environments are different so natural selection favours different characteristics
3- the allele frequencies in the 2 groups shifts in different ways
4- the 2 populations eventually will be unable to interbreed
What is biodiversity?
The variety of all life on earth
What is included in the meaning behind biodiversity?
- number of different ecosystems (ecosystem diversity)
- number of species (species diversity)
- number of individuals in a species
- genetic variation within each species (genetic diversity)
What is the gene pool of a species?
All the genes in that species
Do all the members of the same species have the same genes and alleles.
They have the same genes but different combinations of alleles
What is the definition of genetic diversity?
The number of different alleles within a species’ gene pool
What is meant if a species has a small gene pool?
The species is therefore less genetically diverse (fewer alleles) eg cheetahs who are all almost genetically identical
What may reduce genetic diversity?
Selective breeding, as it only selects a specific few desired alleles to be passed on the the offspring
Farm animals and crops are often selectively bred lowering their genetic diversity, why is this bad?
- all susceptible to 1 disease
- susceptible to an environmental change
What is species diversity?
The variety of species in a community
What is species richness?
Number of species in a sample
What is species abundance? (Same as species evenness)
Number of individuals in a species
What is a good measure of species diversity?
Simpson’s diversity index
What does a higher value of D (Simpson’s index) mean?
The greater the biodiversity
Will deserts have a high or low Simpson’s index’s?
Low
