Evidence for evolution: Chapter 8 Flashcards
Natural Selection
(Links, Based on, Next generation)
- Links all species to a common ancestor
- Based on the observation that individuals in a population showed variation in their characteristics
- Those with beneficial traits to their environment have a better chance of survival and will pass on beneficial traits to next generation and accumulate over time.
Theory of natural selection is based off four observations…
-Variation: occurs in species, with individuals varying in size, colour, camouflage, ability to escape predators, resist disease.
-Competition: based on the idea that life is an ongoing struggle to survive and that organisms compete for resources, mates and space.
-Survival of fittest: individuals who compete successfully for resources are more likely to survive and pass on their traits to next generation.
-Adaptation: adaptations are characteristics best suited o environment. Organisms reproduce and pass on these favourable traits, adaptations.
homologous structures
anatomical structures common to more than one species, inherited from a common ancestor but have different functions.
-Divergent evolution (selective pressures) can lead to the development of homologous structures.
- e.g the pentadactyl limb of bats, birds, human arm, crocodile leg
Analogous Structures
are features of organisms that have the same function but different basic structures that evolved independently, with different ancestry origins.
- often result of convergent evolution
- e.g octopus eye and vertebrae eye
Vestigial homologous structures
homologous structures stemming from a common descent, that no inter gave any functional use for an organisms.
e.g pelvic bone of a whale, human appendix, tailbone.
Convergent Evolution
occurs when distantly related organisms evolve similar adaptations in response to living in the same environment.
e.g anteaters, many animals who eat anything have developed similar structures, even though not closely related or sharing a recent common ancestor.
Divergent Evolution
- species sharing a common ancestor become more distinct due to different selection pressures, gradually leading to speciation over evolutionary time period.
homologous structures could indicate? (what kind evolution0
- homologous structures indicate divergent evolution, because new species have the same fundamental structural plan, but structures may perform a different function
Adaptive Radiation
- As members of the population develop adaptations, by natural selection favouring certain mutations over successive generations, they may diverge enough to become new species.
- extreme case of divergent evolution
- E.g finches of Galápagos Islands
Transitional Forms
- transitional forms exhibit common traits found in both ancestral form and the more modern species.
- they give use evidence for evolution of major groups, documenting change over time on a broad scale.
Comparative dating (Relative dating)
- used to determine the age of a rock or fossil contained in a rock, relative to other rocks or fossils nearby. (superposition)
Absolute Dating
- any technique that assigns a numerical age in years to a fossil or rock.
- Radiometric Dating: uses the known rates of decay of naturally occurring radioactive isotope present in a rock or fossil. (E.g Carbon-14: half life of 5730 years)
Embryology
study of anatomy of embryos and how they develop over time.
- used to establish evolutionary relationships and common ancestry
- early in their development embryos show homologous features that aren’t observed or obvious in adults, as embryo develops, traits complimentary to their environment become more prevalent.
Comparative studies of proteins
analysis of similarities and differences in the sequences of amino acids of the same proteins found in different species.
- enables biologists to obtain a measure of the relatedness between species
common ancestor
an ancestor that is shared by different species
Allopatric speciation
- gene flow is disrupted when populations become physically seperate through geological isolation causing populations to diverge.
Sympatric speciation
- species diverge without any obvious physical or geographical isolation
- evolution of two or more species from a single population within the same place
- could be due to population feeding on different things, choice of mates based on different characteristics
Species
group of organisms that can interbreed to produce fertile offspring naturally.
Speciation
formation of a new species, from one specialist diverging into two or more species.
Pre-zygotes isolating mechanisms
prevent organisms from being able to to interact to reproduce.
- temporal, behavioural, morphological
temporal mechanisms
individuals may breed during different seasons of the year or times of the day.
behavioural mechanisms
individuals may have different courtship patterns
Post Zygotic Isolating Mechanisms
Mechanisms that do not prevent mating from occurring but do prevent young from being produced.
Gamete Mortality
- Post reproductive isolating mechanism
- gametes do not survive
Zygote Mortality
- Post reproductive isolating mechanism
- the zygote forms but does not survive
Hybrid sterility
- Post reproductive isolating mechanism
- adult offspring are formed but are infertile because they are unable to produce viable gametes, usually because of having received a different number or type of chromosomes from each species
Microevolution
- any change in allele frequency in a gene pool of a population overtime, within a species
- occurs in a population due to changes; mutation, selection (natural and artificial) genetic drift and gene flow
Macro evolution
- major evolutionary changes above the species level.
- large changes in gene pool can lead to production of new species (speciation)
