Evolution Flashcards
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What is a scientific theory?
A scientific theory is a well- substantiated
explanation of some aspect of the natural world,
based on a body of facts that have been repeatedly
confirmed through observation and experiment.
Evolution is a scientific theory.
Steps for developing scientific theories:
- Completed through reasoning, inferences of
data. - Testing – observations of the natural world.
- Peer review.
What is evolution?
Evolution is the genetic changes in a population over a very long
period of time.
What is a population?
A population is a group of
a particular species living in
the same geographical
area at the same time.
What is a gene pool?
A gene pool is all the different types of
genes in a population.
Within a species there is genetic variation
within the gene pool.
Individuals have the same number of
genes but differing alleles.
Evolution can take place through five key mechanisms which
change the genetic make-up of a population by increasing the
variation or selecting for the variation. What are they?
Mutation
Sexual reproduction
Gene flow
Genetic drift
Natural selection
Mutation:
- Give rise to new alleles.
- Increase the genetic variation within
a population if the mutation is
advantageous. - Harmful mutations are often not
passed on.
Sexual reproduction:
- Meiosis creates new combinations
of alleles. - Non-random mating – certain traits
(alleles) are selected for. - Increases variation to populations
Gene flow:
- Gene flow is the movement of genetic
information from one population to
another of the same species. - Increases genetic variation within
populations.
Genetic drift:
- Genetic drift is the random
change in an allele frequency in a
population. - Natural disasters can rapidly
decrease numbers in a population. - The phenotype of individuals don’t
assist their survival survival is
by chance.
Natural selection:
- Natural selection is the principal
mechanism for evolution. - Survival of the fittest.
- Relies on variation being in the
gene pool of population and a
selection pressure acting on it.
What are selection pressures?
Selection pressures are factors which affect the survival
of individuals.
Steps of natural selection
The steps of natural selection are:
1. Variation naturally exists in the population (sexual reproduction,
mutations and gene flow)
2. The alleles of some of the organisms in the population are expressed
in favourable traits better adapted.
3. Individuals with favourable traits are selected for and they are more
likely to survive and reproduce than others of their species.
4. Over time, the individuals with the favourable traits pass on their
alleles and become more numerous in the population.
Adaptations
- Adaptations are characteristics that make an individual suited to
its environment and way of life - Adaptations are determined by genes and may be passed to
offspring.
Species
A species is a population that can breed and produce fertile
offspring.
* Hybrids exist but cannot reproduce.
Biological fitness
Is the ability of a particular genotype to contribute to
subsequent generations.
* More offspring = higher fitness.
Directional Selection
The process of natural selection favouring a particular
phenotype.
* e.g. camouflage, insecticide/antibiotic resistance
The environment chooses the best suited organsism.3333
Artificial selection
Artificial selection is the intentional (selective) breeding of plants
and animals to produce desirable traits:
* Aesthetics
* Increase food production
* Improve flavour
* Drought resistance
Natural vs. artificial selection
Natural Selection:
Trait is selected for by
being the best
adapted
Trait increases the survival
of species
Artificial Selection:
Trait is selected for by
humans
Trait may not increase the
survival of species
Both:
Variation exists
naturally
Traits and alleles are
inherited from parents
Changes occur over
many generations
