SBI3U Evolution Test #1 Flashcards
Define fitness
The sustainability of an organism to its environmental conditions.
Define selective pressure
Environmental condition(s) that select for certain characteristics of individuals and select against others.
Define natural selection
The process whereby the characteristics of a population of organisms change because individuals with certain heritable traits survive specific local environmental conditions.
Define Evolution
The relative change in the characteristics of populations that occurs over successive generations.
What are some modern examples of evolution?
Bacteria, mosquitoes (those resistant to DDT grow and thrive in the population - pesticides no longer work), coral reefs (adapting to heat stress/global warming over time), super weeds (over-use of pesticides), and varolla mites on bees (have developed resistance to chemical pesticides that were used to control them).
What are the 3 requirements for evolution to happen?
- Time - lots of time (or at least many, many generations). 2. Genetic variation - a variety of alleles in the genetic make up of the population 3. Pressure from the environment - something that causes some to survive and some to not.
What is micro-evolution?
This is the evolutionary change within a species.
What is macro-evolution?
These are changes that take place over long periods of time, changes in kinds of plants and animals on earth.
What is genetic variation?
Genetic variation is a variety of alleles in the genetic make up of the population.
Define homologous structures.
Body parts in different species that have the same evolutionarly origin but have different structures and functions.
Define analogous structures
Analogous structures are body parts in different species that have a similar function, but evolved differently.
Define convergent evolution
This is the evolutionary process in which similar traits arise in 2 or more species because each species has independently adapted to similar environmental conditions, not because they share a common ancestor. The organisms are unrelated, but occupy the same niche in very different geographical regions and have similar structures/functions.
Define divergent evolution
This is the process by which species that were once similar to an ancestral species become increasingly different. They become different through adapting to different habitats and food sources and eventually become their own new species.
Define vestigial structures
These are body parts that were functional in a species’ ancestors, yet appear to have no current function, e.g. pelvic bones in baleen whales.
Define embryology
This is the study of embryos.
Define co-evolution
This is the evolutionary process in which two species of an organism are tightly linked and evolve together, each population responding to the changes in the other population, e.g. plants and their pollinators.
Define speciation
This is the formation of a new species.
Define prezygotic barrier
A prezygotic barrier is a factor that prevents mating between two species, or that prevents fertilization if individuals from different species do attempt to mate. Pre-zygotic barriers include behavioural isolation, temporal isolation, mechanical isolation, and gametic isolation.
Define sympatric speciation
This is the differentiation of populations within the same geographic area into species.
Define post-zygotic barriers
A factor that prevents hybrid zygotes from developing into normal fertile individuals. Includes hybrid inviability, hybrid sterility, and hybrid breakdown.
Define allopatric speciation
This is the formation of a new species that occurs when a population is split into two or more isolated groups by a geographical barrier.
Define gene flow
This is the movement of new genes into a gene pool. This movement can reduce differences between populations that were caused by isolation and genetic drift.
Define the bottleneck effect
This is the effect that occurs when a population is greatly reduced by events such as natural disaster or overhunting, resulting in certain alleles being overrepresented and other alleles being underrepresented or absent in the population, due to chance. The effect leads to a genetic drift and decreased genetic variation in the population.
Define the founder effect
This is the cause of genetic drift due to small group of individuals colonizing a new area; the small group probably will not contain all the genes represented in the parent population.
Define non-random mating
Any situation in which individuals do not choose mates on a random basis, such as mating based on proximity, relatedness, or similarity of phenotype.
Define assortive mating
A type of non-random mating in which individuals choose partners that have similar phenotypes.
Define stabilizing selection
Natural selection that favours intermediate phenotypes and acts against extreme variants.
Define directional selection
This is selection that favours the phenotypes at one extreme over another, resulting in the distribution curve of phenotypes shifting in the direction of that extreme.
Define disruptive selection
Selection that favours the extremes of a range of phenotypes rather than intermediate phenotypes. This type of selection can result in the elimination of intermediate phenotypes.
Define sexual selection
Selection for mating based, in general, on competition between males and choices made by females.
Name the 5 types of pre-mating isolation and briefly explain the meaning of each
- Geographic (individuals are geographically separated from each other)
- Ecological (individuals have different habitats from each other, e.g. in a tree vs. on the ground)
- Temporal (the species are not compatible, e.g. have different mating seasons)
- Behavioural (they have different mating rituals from each other)
- Mechanical incompatibiliy (sexual reproduction organs do not “fit” together
Name and briefly explain the 3 types of post-mating/post-zygotic isolation.
- gamete incompatibility (the sperm cannot fertilize the egg)
- hybrid inviable (egg can be fertilized, but no offspring can be produced)
- hybrid infertile (offspring can be produced, but is infertile)
Define species
A group of individuals that actually or potentially interbreed in nature (the biggest gene pool possible under natural conditions).
Name what evolutionary process causes new species to form
Two populations reach the point where they are no longer able to mate, resulting in reproductive isolation.
What must be true in order for species to remain distinct?
What is the cause of speciation?
Gene flow reduction
Define sympatric speciation
Two populations live in the same area but are reproductively isolated (usually happens) in plants, occasionally happens with animals (because of specialization of range/food supply)
Define allopatric speciation
Two populations are physically separated, then the species become diverse due to natural selection (i.e. salamanders)
Define instantaneous speciation
Occurs in one generation due to major changes in the chromosome numbers (polyploids, chromosome fusion or fission) - most happen in plants
What is the only source of new genetic material in a population?
Mutations
What quality of mutation increases reproductive success?
Only beneficial mutations
Define genetic drift
This is the change of frequencies of particular alleles in a small population, caused by chance alone. Changes can be drastic.
Name 4 mechanisms for genetic variation
Gene flow, mutations, natural selection, genetic drift (bottleneck effect and founder effect).
Define sexual dimorphism
This is the difference between the phenotypes of males and females of the same species.
Define structural adaptations
Physical features like anatomy, colouring, and appearance that allow for an organism to be better suited and more fit for its environment.
Define physiological adaptations
Alterations in functions that allow for increased success in the environment they live in, e.g. humans produce hormones to help them react in stressful situations - increasing heart rate, respiratory rate and improve vision.
Define behavioural adaptations
- actions taken by the organisms that allow for greater success
- actions are taken all for different reasons
- migration courtship, foraging, defense
- movement in large groups
Define anatomical clues
Comparison between anatomical features in related or unrelated species are explained as homologous or analogous features.
State two evidences in DNA for evolution.
- the relationship between closely related species is clearly evident when DNA comes to light
- the more similar the DNA sequence between species the more closely related they are in evolutionary history
