Evolution by Natural Selection Flashcards
Define evolution
Change over time
Define biological evolution
Genetic changes in a population that are inherited over successive generations due to natural selection and ultimately resulting in the formation of a new species
Evidence of evolution (5)
- Fossil records
- Modification by descent
- Biogeography
- Genetics
- Other
Define fossil record
The accumulation of all listed and known fossils of different ages
Geological timeline (4)
- Archaeozoic
- Palaeozoic
- Mesozoic
- Cenozoic (now)
Define modification by decent
How different plant and animal groups were modified to adapt to their different environments
Homologous structures
Similar structures with the same body plan that perform different functions
Homologous structures in vertebrates
Pentadactyl limb
Analogous structure
Body parts that perform the same function, but did not originate from a common ancestor
Biogeography
The study of the distribution of plant and animal species in specific geographical regions
Genetics
The study of inheritance
Genetics evidence (4)
- Closely related organisms have similarities in their DNA
- Explains source of variation
- Shows how changes in genotype/phenotype are transferred
- Explains how gene pools change
Other forms of evidence (3)
- Comparative biochemistry
- Vestigial organs
- Comparative embryology
Erasmus Darwin’s Theory
Life originated from a common ancestor. One species developed from another over time.
Jean Baptiste de Lamarck’s Theory
During their lifetimes, organisms acquire changes in characteristics that are inherited by their offspring
Alfred Wallace’s Theory
Worked with Charles Darwin, on natural selection
Charles Darwin’s Theory (8)
- Organisms produce a large number of offspring
- There is variation in the offspring
- Some individuals have favourable characteristics that give them an advantage
- Organisms with favourable characteristics are better adapted to survive
- Organisms with less favourable characteristics die
- Survivers reproduce, and pass on favourable characteristics
- Next generation has higher proportion of favourable organisms
- Changes lead to formation of new species
Define natural selection
The mechanism of evolution where nature selects the fittest individuals for survival
Conditions for natural selection (4)
- Variation in population
- Characteristics must be hereditary
- More offspring than necessary
- Changes in environment
Define artificial selection
The deliberate breeding of plants and animals for desired characteristics that would not necessarily benefit the survival of the offspring
Define speciation
The formation of species increases the range of organisms on earth and thus increases biodiversity
Define extinction
The loss of species decreases the range of organisms on earth and thus decreases biodiversity
Define reproductive isolation
The type of isolation that develops between the new species and the ancestral species, and prevents inbreeding
Causes genetic variation in species (2)
- Genetic recombination
- Mutations
Genetic recombination
Occurs during meiosis and sexual reproduction
Types of mutations (2)
- Gene mutations
- Chromosome mutations
Types of gene mutations (3)
- Harmful mutations
- Neutral mutations
- Beneficial mutations
Genotypic variations in populations examples
- Galapagos finches
- White lions
Define Inbreeding
The crossing of closely related individuals
Advantages of inbreeding (3)
- Produces predictable offspring
- Recessive genes can be isolated
- Undesirable characteristics and be isolated
Disadvantages of inbreeding (8)
- Offspring have low resistance to disease
- High mortality rate
- Increased abnormalities
- Recessive genetic diseases evident
- Loss of vigour in offspring
- Decrease in frequency of heterozygous gene pairs
- Offspring can be sterile
- Gene pool is smaller, possibility of extinction
Define Outbreeding
The crossing of unrelated individuals resulting in offspring that are genetically different
Advantages of Outbreeding (4)
- New characteristics introduces, gene pool enlarges
- Reintroduces lost characteristics
- Increases hybrid offspring
- Individuals still ‘pure’
Disadvantages of outbreeding (3)
- Typical characteristics lost
- Loss of separate race, new race develop
- Less predictability in offspring
Convergent evolution
Many different, unrelated organisms independently developing adaptation for similar environments
Divergent evolution
One common ancestor giving rise to a variety of different, but related organisms
Mechanisms of speciation (2)
- Geographic (allopatric) speciation
- Sympatric speciation
Allopatric speciation
When a new species arises from an existing species when the populations are separated by a geographical barrier
Sympatric speciation
When a new species arises from an existing species in the same geographical area
Mechanisms of reproductive isolation (3)
- Temporal/seasonal isolation
- Behavioural isolation
- Mechanical isolation
