Evolution

species

organisms with similar characteristics that can reproduce and produce fertile offspring.

speciation

formation of a new species

Charles Darwin

proposed the theory of evolution after many scientific studies of organisms including finches.

"the survival of the fittest"

Darwin’s theory - involves only the organisms with characteristics that enable them to survive in their environment passing on their genes to the next generation.

“fittest”

certain characteristics favour survival.

natural selection

process by which favoured characteristics increase the likelihood of survival in the presence of certain selection pressures.

first understanding of natural selection

variation exists in a population.

selection pressures

environmental factors (abiotic and biotic) that determine whether characteristics are favourable for survival.

who opposed the theory of evolution

Some religious beliefs and the theory of evolution opposed each other and thus religion and most of society put up much resistance to the theory of evolution.

why was the theory of evolution accepted

more evidence has been uncovered over time. - many forms of scientific evidence.

evidence of evolution

fossils, anatomical similarities, embryology, biogeography, and genetic relatedness.

what are fossils

exist as actual remains, hard parts of the organism, impressions or indirect evidence such as footprints.

what does fossilisation require

requires remains being quickly covered with sediment and a lack of oxygen.

estimating age of fossils

relative dating - estimates the age of the fossil by layer of earth it is in and using the other fossils also in that layer.

absolute dating - radioactivity/radio isotopes - estimates the age of fossils by comparing the ratio of the radioactive isotopes to other isotopes.

biogeography

the process of studying the geographical distribution of living species and fossils, used as evidence of evolution.

continental drift

the moving of the tectonic plates and the distribution of fossils, animals and geological substances has allowed this to be mapped.

comparative anatomy

Related species often have similar structures (anatomically similar) so comparative anatomy can be used as a way of determining relatedness

Homologous structures

similar structures that are found in different organisms that indicate a common ancestor.

e.g. The pentadactyl limb is an example of a homologous structure - wings, arms, fins.

anatomical structure…

Anatomical structure relates closely to function.

Vestigial structures

anatomical structures that are no longer used but remain.
may be similar to functioning structures in other species and can indicate a common ancestor.

e.g. appendix

Comparative embryology

involves comparing embryos at different stages and similarities indicate a common ancestor.

At different stages of embryo development, similarities can be observed between species.

biochemistry/genetics

The greater percentage of amino acids (in a protein) or DNA bases in common between species, the more closely related the species are.

Divergent evolution

when members of a species are separated (usually a geographical barrier) and can't interbreed, so they evolve differently due different selection pressures.

e.g. Darwin's finches

Convergent evolution

when unrelated species have similar characteristics due to a common environment.

e.g. fins of sharks and dolphins

Analogous structures

similar structures that perform the same role, but have evolved in unrelated species

convergent evolution, e.g. bat and butterfly wings

Phylogenetic trees

show the speciation events over time and provides information on the relatedness of species - the more recent the branching the more closely related.

The lengths of lines in a phylogenetic tree represent time. If the line doesn’t continue to the present day the species underwent extinction.

Artificial selection

when humans use selective breeding techniques to breed organisms with desirable features.

artificial selection changes

generally results in faster changes to the percentage of organisms with the desired characteristic than natural evolution.

can result in less genetic variation and can amplify other characteristics which may be a disadvantage to the species.

things to know (4)

1. A species evolves over time due to characteristics being favoured by selection pressures increasing the chance of survival. It is not individuals that change.

2. Genetic diversity helps a species to survive changes in selection pressures due to variation that already exist in populations.

3. Evolution is ongoing.

4. Humans may be able to assist in the conservation of species by understanding the impact of selection pressures on species.

how to answer natural selection questions

1. population has variation

2. selection pressure

3. some variations are favourable

4. more offspring are produced with favourable offspring

5. a population will change over time