Evolution Flashcards
Adaptation
A structure, behaviour, or physiological process that helps an organism survive and reproduce in its environment
Allopatric speciation
When a population is split due to some geographical barrier which prevents members of two groups from reproducing together
Analogous structures
-different structures, similar function
-organisms are NOT closely related. However, they have evolved a similar “solution” to a problem
Artificial selection
Occurs in captivity rather than a natural setting. Humans chose the traits THEY wish to see in the offspring and breed only those individuals that show the trait
Bottleneck effect
A population is greatly reduced due to a catastrophic event, resulting in certain alleles being over or under-represented
Directional selection
-favours phenotypes at one extreme or another
-causes a shift in the distribution curve
-common during times of environmental change
Disruptive selection
Favours extreme phenotypes rather than intermediate ones
Evolution
A scientific theory that describes changes in a species over time
Fitness
The contribution that an individual makes to the next generation by producing offspring that will survive long enough to reproduce
Founder effect
A small group of individuals colonizes a new area, and usually do not contain all of the alleles represented in a parent population
Gene flow
-describes the movement of alleles from one population to another (migration)
-introduces new alleles to the population, similar to mutation
Gene pool
The gene pool of a population includes all of the alleles for all of the genes of each individual in the population
Genetic drift
-the change in the frequencies of certain alleles in a small population, caused only by chance.
-alleles appear to “drift” or disappear out of the population, and become lost
-two particular situations lead to genetic drift: the bottleneck effect and the founder effect
Hardy-Weinberg law
States that the original genotype proportions will remain constant from generation to generation as long as the following conditions are met: the population must be large, random mating must occur, no mutations must occur, isolation, no natural selection(no genotype can have a reproductive advantage over another)
Hardy Weinberg principle (equations)
P^2 + 2pq + q^2 = 1
P + q = 1
Homologous structures
-similar structures, different functions
-evidence of a common ancestor
Macroevolution
-occurs when members of a population may change so much that they are no longer capable of producing viable, fertile offspring with members of the original population
-when this happens, speciation has occurred
Micro evolution
Changing the percentage or frequency of certain alleles within a population leads to evolution within a population
Natural selection
The process by which characteristics in a population change over due to the ability of some organisms to survive and reproduce better than others because of the traits they have inherited
Phyletic evolution
A pattern of evolution in which the entire population becomes different from the ancestral population, such that there are no members of the original population left
Pre zygotic isolating mechanisms
Behavioural, temporal, ecological/habitat, mechanical, gametic isolation
Post zygotic isolating mechanisms
Hybrid breakdown, hybrid inviability, hybrid infertility
Stabilizing selection
-favours intermediate phenotypes
-selects against extremes, therefore reduces variation
-human birth weight is an example
Vestigial structures
Structures that have become reduced in appearance or function over time
Morphological species
A group of individuals that have similar physical traits
Biological species
-A group of individuals that can interbreed in nature and form viable, fertile offspring
-this is the most widely used definition of species
Phylogenetic species
The smallest group of individuals that share a common ancestor, forming one branch on the tree of life
Speciation
-the formation of new species from existing species
-it is sometimes referred as macroevolution. It begins with micro evolution.
Pre-zygotic (definition)
Prevent formation of a zygote
Post-zygotic (definition)
Prevent zygotes from forming viable, fertile offspring
What is a zygote
A fertilized egg
Behavioural isolation
Different species use different courtship and other mating clues to find and attract a mate
Temporal isolation
Different species breed at different times of the year
Ecological/habitat isolation
Very similar species may occupy different habitats within a region
Mechanical isolation
Difference in morphological features may make two species incompatible
Gametic isolation
Make gametes may be unable to recognize/fertilize an egg of a different species.
Hybrid inviability
Zygote development is not successful, and the hybrid dies before birth.
Hybrid sterility
Hybrid is viable but is sterile
Hybrid breakdown
First generation hybrids are viable and fertile. However, when hybrids mate their offspring are either sterile or weak
Divergent speciation
-a pattern of evolution in which species that were once similar become increasingly different
-eventually there is no gene flow between populations
Sympatric speciation
When populations within the same geographical area become unable to reproduce together (common in plants)
Convergent speciation
A pattern of evolution in which similar traits arise because species have independently or separately adapted to similar conditions
Mutation
-provide new alleles in a population and therefore allele frequencies change
-mutation alone cannot cause evolution (it must provide a selective advantage)
Non-random mating
-random mating describes a pattern where any sperm had an equal chance of fertilizing ANY egg in the population
-random mating is rare; individuals usually mate with others in close proximity, or choose mates based on physical/behavioural characteristics(phenotypes) which is not random
Fossil evidence
-fossils are the remains one impression of a prehistoric organism embedded in rock
-they are evidence of species that existed in the past
-problem: fossils preserve hard structures well, but not soft tissues
^- they only give only a “snapshot” of ancestral forms, but don’t show all changes or details
Transitional fossils
-Fossils that show links between groups of organisms
-help to show how organisms changed over time
Biogeography
The study of the distribution of organisms around the world
Evidence from biogeography
-animals found on islands often closely resemble animals found on the closest mainland
-areas that are close together tend to have related species, even if their environments are very different
-fossils of the same species can be found on the coastline of neighbouring continents
Evidence from comparative anatomy
Homologous structures, analogous structures, vestigial structures
Evidence from comparative embryology
Embryos of different organisms show similar stages of development, indicating common ancestry
Evidence from molecular biology
-the nuclear components that make up all organisms are the same
-in bacteria, plants, animals, and humans, DNA is made of the same 4 nucleotides, and all the proteins are made from combinations of the same 20 amino acids (although several hundred other amino acids do exist)
-this in itself suggests common ancestry
Consequences of artificial selection
Inbreeding animals can cause some undesirable consequences while selecting for certain desired traits
5 points of Darwin’s natural selection
-populations have variations
-some variations are favourable to survival
-due to limited resources, more offspring are produced than can survive
-those that survive have favourable traits, and will pass those favourable traits on
-a population will change over time
Harmful mutations
-produce a change in the individual’s phenotype that reduces the reproductive success of the individual
-the mutation that causes breast cancer
Neutral mutations
-that provide no benefit or harm to the individual
-the mutations resulting in different colours of eyes
Beneficial mutations
-produce a change in the individual’s phenotype that gives the individual an advantage in survival and/or reproduction
-the mutation that allows humans to digest cows milk (lactose tolerance)
-the mutation which causes some animals to be born with more fast-twitch muscle fibres than others (making them faster)
Selective advantage
Something that improves an organism’s chance of passing on their traits
Cuvier
-using palaeontology he could see past versions of species, seen how they change and disappeared.
-came up with catastrophism - the idea that catastrophes destroyed species living in a particular region, allowing species from neighbouring regions to repopulate the area
Lyell
-created uniformitarianism - evolution is happening constantly at the same rate over long periods of time
Lamarck
Characteristics acquired during an organism’s lifetime could be passed on to its’ offspring
Darwin
Natural selection
