Evolution Flashcards
(30 cards)
What is variation?
The presence of variety; physical and genetical differences between members of different species as well as members of the same species.
What types of variation are there?
- Continuous variation.
- Discontinuous variation.
- Intraspecific variation.
- Interspecific variation.
What is intraspecific variation?
Variation between members of the same species.
What is interspecific variation?
Variation between members of different species.
What is continuous variation?
Variation in which there is a full range of intermediate phenotypes between 2 extremes.
What are the characteristics of continuous variation?
- Significantly affected by environmental influences.
- Quantitative.
- Combined effect of many genes (polygenetic inheritance) with different alleles, each having a small effect.
- Complete range of measurements from one extreme to another.
- Data can be plotted on frequency histogram.
- Data plotted usually forms a typical bell shaped curve (normal distribution).
What is discontinuous variation?
Variation in which there are discrete groups of phenotypes with no or very few individuals in between.
What are the characteristics of discontinuous variation?
- Controlled by alleles of a single gene or small number of genes.
- Features cannot be measured across a complete range.
- Qualitative.
- Individuals fall into a distinct category.
- None/little environmental influences.
- Data can be plotted as bar charts.
- Data is discrete/categorical.
What are some examples of continuous variation?
Humans: - Height. - Mass. Plants: - Width of leaves. - Mass of fruit. Microorganisms: - Diameter. - Lifetime. - Length of flagellum.
What are some examples of discontinuous variation?
Humans: - Blood group. - Hair colour. - Eye colour. Plants: - Colour of flower. - Flowering/non-flowering. Microorganisms: - Presence of flagellum. - Parasitic/free-living.
What causes variation?
Genetics: Many of our characteristics (phenotypes) are determined by the genes we have (genotype). A lot of the time, a combination of genes are responsible for one characteristic. Within this combination are different alleles of the same gene that create variation.
Environment: Environmental factors can influence which genes are active at a particular time. For example, a person exposed to sunlight regularly may become tanned as a result of the sunlight activating a gene responsible for producing dark pigments in the skin.
What is a adaptation?
A variation which helps an organism survive and thrive in the environment they live in.
What are the features of a well-adapted organism?
They are able to:
- Gather enough food by autotrophic or heterotrophic means.
- Find enough water.
- Defend itself from predators and diseases.
- Survive the physical conditions of the environment, e.g. temperature, light, amount of water…
- Respond quickly to changes.
- Have enough energy and nutrients in excess to reproduce successfully.
What are behavioural adaptations?
Things that an organism chooses to do which enhances their chances of survival. For example, killer whales hunt in packs in order to increase chances of success against preys.
What are physiological adaptations?
Things that the body/cells in the body of the organism does in order to enhance their chances of survival. For example, chemical reaction in lure of anglar fish produces a light used to attract their prey.
What are anatomical adaptations?
Feature of the body of the organism that are adapted especially to enhance the chances of survival. For example, killer whales have fat layer of blubber underneath skin used as insulation in the cold.
What were Darwin’s 4 observations?
- No two individuals are identical.
- Populations in nature tend to remain fairly stable in size.
- Offsprings generally appear similar to their parents.
- Organisms have the ability to produce large numbers of offsprings.
What were Darwin’s 3 conclusions?
- There is a struggle to survive: Too many offsprings are produced each generation (Organisms have the ability to produce large numbers of offspring), so there is fierce competition for food and resources; only a small proportion of offsprings live to reproduce (Populations in nature tend to remain fairly stable in size).
- Better adapted individuals survive and pass on their characteristics: Some individuals are more adapted to the environment than others due to chance mutations (No two individuals are identical), so they outcompete the less well adapted and live to reproduce, passing on their characteristics to their offsprings (Offsprings generally appear similar to their parents).
- Over time, a number of changes may give rise to a new species: Over a long time, these small variations may accumulate in a group of organisms of the same species until they become so different that they are no longer able to interbreed with the rest of the population, and become a new species.
What is natural selection?
The selection by the environment of particular individuals that show certain variations through selection pressure. These individuals will survive to reproduce and pass their variations to the next generation.
What are some examples of selection pressures?
- Availability of food: Individuals that are able to eat the food available in the environment have the selective advantage.
- Predators: Individuals who can avoid being seen or are able to run away from predators have the selective advantage.
- Disease: Individuals that are resistant to a disease is more likely to survive during an outbreak.
- Environment: Individuals that are able to cope with the conditions in the environment have the selective advantage.
What is speciation?
The formation of a new species.
What conditions must be present in order for speciation to occur?
- There must be some form of a reproductive barrier.
- 2 groups of the same species are reproductively isolated from each other so that they are unable to interbreed and there are 2 gene pools.
- Variation in one gene pool cannot spread throughout the whole species.
- The 2 groups slowly change according to the different selection pressures present in the 2 environment.
- Eventually, the 2 groups may become so different from each other that they are no longer able to interbreed to produce fertile offsprings.
What is allopatric speciation?
A geographic reproductive barrier that prevents 2 or more groups of the same species from breeding freely from each other. For example, different groups of the same species on different islands, separated by the ocean.
What is sympatric speciation?
A reproductive barrier that arises within the population, for example:
- Behavioural: Different members may become active at different times of the year.
- Physical: Reproductive parts of individuals may become incompatible.
