Evolution and Biodiversity Flashcards
Species
A group of organisms that can interbreed and give fertile offspring.
Population
A group of individuals of the same species living at the same area at the same time.
Gene Pool
All the possible genes and their alleles within a species.
Speciation
The process where a new species is formed from a pre-existing species.
Evolution
A gradual change in the heritable characteristics of an Individual.
Directional Selection
Selection that favors individuals on one end of the phenotypic distribution.
Individuals not favored die out.
Increase in dark moths during industrial revolution, when the pollution caused darkening of the trees, so the white moths
were more visible to the predators.
Stabilizing Selection
Selection that favours individuals in the middle of the phenotypic spectrum.
Both extremes in the spectrum of a characteristic are not favoured by the environment.
Sickle cell anaemia. Individuals that are homozygous either for healthy cells, or sickle cells will be exterminated in the areas exposed to malaria.
The heterozygous individuals will have both resistance to malaria and a decent oxygen carrying capacity to be favoured by the environment
Disruptive Selection
Eliminates individuals with the intermediate characteristics.
Only both ends of the phenotypic variation will be favored by the environment.
Squirrels with long tails are good at balancing themselves on the trees, squirrels with short tails are faster at running away from predators on the ground.
The squirrels that have intermediate tails are easily caught by the predator on the ground, but also on the trees, as their balance is not as good
Temporal - Reproductive Isolation
Occurs when two populations stop interbreeding because of differences in their mating times.
Maggot fly, which in North America used to leave its eggs on the hawthorn fruits, which were the food for its larvae.
With the introduction of non-native apple trees, it started leaving eggs on those as well.
However, since the two fruits ripe at different times, depending on which fruit the fly leaves its eggs, it will mate at different times.
Therefore within the population, there is a temporal mating barrier.
Behavioural -Reproductive Isolation
Geographical - Reproductive Isolation
Individuals of the same population become
separated geographically and can therefore not mate anymore.
Lava lizards from Galapagos. A group of lizards managed to get from one
island to another
As they couldn’t return anymore, they could only interbreed
with the population that went to the island.
Over time, the interbreeding of
the lizards on one, and on the other island, created two different species of lizards.
Geographical - Reproductive Isolation
Individuals of the same population become
separated geographically and can therefore not mate anymore.
Lava lizards from Galapagos. A group of lizards managed to get from one
island to another
As they couldn’t return anymore, they could only interbreed
with the population that went to the island.
The interbreeding of the lizards on the other island, created two different species of lizards.
Gradual and Abrupt Speciation
There are full fossil records showing the gradual change of species over time.
Environmental pressures and species adaptation would eventually lead to accumulation of new characteristics that differ one older species from a newer one.
There are incomplete fossil records where the lack of intermediate fossils could be explained by a more abrupt evolution.
This could happen through genetic mutation, like doubling of the chromosome numbers that result in organisms that are incompatible with their parental species.
Polyploidy is an example
Polyploidy
Individuals of the same species have the same number of chromosomes.
Non-disjunction of chromosomes during meiosis may result in gametes with double the number of chromosomes.
If such a gamete is fused with a normal, haploid gamete, the offspring
become triploid, and therefore infertile since they cannot divide their chromosomes in half.
Results in a new species since its individuals cannot mate with other members of the species and produce fertile offspring.
Evolution
Accumulation of changes in heritable characteristics of a species over time.
Over time, certain characteristics of a species change, and if these
characteristics are inheritable, then this change is transferred to all the subsequent
generations.
Adaptation
The process of change by which an organism or species becomes better suited to its environment.
If the members of species become separated for a long period of time, due to adaptations in their new environment will start changing as well.
Sometimes it happens that these two populations change so much that, even if they got reunited, they would not be able to interbreed anymore.
Pentadactyl Limb
Amphibians, reptiles, birds &
Pentadactyl Limb
Amphibians, reptiles, birds &
Pentadactyl Limb
Amphibians, reptiles, birds &
Pentadactyl Limb
Amphibians, reptiles, birds &
Pentadactyl Limb
Amphibians, reptiles, birds & mammals use their limbs fro running, walking, swimming or jumping
The basic bone structure of this limb is the same in all vertebrates, pentadactyl limb
They probably shared the same ancestor, and due to their different environments the same limb adapted to suit the type of locomotion. The type of evolution is called adaptive radiation
This example is called homologous structures
These
Selective breeding
Domesticated animals are an example of fast-forwarded evolution
By selective breeding, favorable characteristics for humans were bred with a similar species to get offspring with similar characteristics
A dog, which is a domesticated wolf
Less aggressive wolves were bred until calmer offspring were produced.
Smaller wolves = smaller dog species
Fossil Records
Fossils are remaining of organisms found in stones that can help us determine their age and compare them to the currently living species.
It’s possible to determine the age of stones where fossils were found.
Bacteria are found in the oldest fossils, followed by algae, fungi and more complex organisms later.
Acanthostega is a fossil of vertebrae that doesn’t match any of the current living species, but shows similarities with them.
It has both 4 limbs that matches amphibians, but also a fish-like tail and gills which suggests it was probably a transition species between the fish and amphibians.
Melanism
A lightly colored species has a darker variant.
Biston betularia- peppered moth
Lightly colored moths blend with lightly colored tree branches avoiding predators
The melanistic form cannot blend in with the trees so are frequently eaten.
During the industrial revolution, the smog caused the trees to darken so the lightly colored moths became visible on tree branches and got eaten.
Melanistic form was less noticeable so had a higher rate of survival, and became more prevalent.
The switch from light population to dark population is an example of evolution
Shows how the species changes as a result of a changing environment by passing on its favourable genes.
Natural Selection
Charles Darwin was the first scientist to publish the theory of natural selection,
Alfred Wallace had the same idea at the same time was just too slow to publish.
Natural selection suggests that the better-adapted species will have a higher chance of survival.
Therefore be able to pass on their genes and the species will evolve
towards the better-adapted species.