Evolution Flashcards
Mutagens
Physical or chemical agents that induce mutations in DNA are called mutagens and are said to be mutagenic
Negative consequences of genetic variation
Only a small % cause genetic disorders—most have no impact on health or development.
Positive consequences of genetic variation
A very small % of all mutations actually have a positive effect.
Lead to new versions of proteins that help an individual better adapt to changes in his or her environment.
Eg. a beneficial mutation could result in a protein that protects an individual and future generations from a new strain of bacteria.
Taxonomy
used to determine evolutionary relationships between organisms
Binomial Nomenclature
Naming species: composed of two parts (scientific name)
Carl Linnaeus
Swedish physician and botanist: founder of modern taxonomy.
Jean Baptiste Lamarck:
Evolution by use or disuse
Darwin’s 2 ideas
Evolution, natural selection
Darwin’s 5 points
- Population has variations.
- Some variations are favourable.
- More offspring are produced than survive.
- Those that survive have favourable traits.
- A population will change over time.
Evidence For Evolution
Fossils
Biogeography
Comparative Anatomy
Molecular Biology
Evidence from fossils
Fossils in a particular rock are different from rocks above and below = gives them a certain age
Index fossils
plant and animals species that lived a short time in geological history, but were wide spread
Comparative Anatomy
Comparative anatomy = study of similarities & differences in anatomy of organisms.
Homologous Structures
Similar in structure & development but may have different functions.
divergent evolution
Implies common ancestor
Differences in structure have evolved in response to different environmental conditions.
Analogous Structures
Similar function but no structural relationship.
Convergent evolution
structures with different origins have become adapted to a common function.
Parallel Evolution
Related species evolve similar features independently.
Vestigial Organs
Once useful in an animal’s evolutionary past
Now has no apparent function
Limitations of fossils
soft-bodied organisms do not fossilise easily.
only a small fraction of organisms die in conditions favourable to fossilisation.
only a fraction of the fossils have been unearthed.
What causes natural selection?
Natural selection happens because there is variation i.e. natural differences in populations.
Variation
Variation is caused by differences in genes.
Speciation
When one species splits into two or more separate species.
Steps of speciation
Variation
Isolation
Selection
Physical Isolation
Physical barrier = allopatric speciation
Earthquakes, volcanoes, desert formation
Temporal Isolation
Breeding at different times to other groups inside a species
Behavioural Isolation
Changes in courtship rituals (mating calls)
Mechanical Isolation
Mutations that cause physical incompatibility (body parts of pollinators or potential mates)
Developmental Isolation
Unviable or sterile offspring
gene pool
All the alleles (versions of genes) that exist in a population
Allele frequency
How common an allele is in a population.
Gene Flow
Movement of genes from one population to another – Due to Migration
Genetic Drift
variation in the relative frequency of genotypes in a population (chance, some die or don’t reproduce) – Due to Random Sampling
Microevolution
Survival through the inheritance of favourable traits (genes).
Results in changes
within a population
Macroevolution
Progression of biodiversity over geological time.
Results in new species
