EcologyTest2Studying

EcologyTest2Studying - LECTURE 7 POPULATION DISTRIBUTIONS...

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LECTURE 7 – POPULATION DISTRIBUTIONS AND ABUNDANCE * What factors typically limit species distribution? - Environment - No species can tolerate the full range of the earth’s environments - Adapted to a particular environment…climate may influence directly, but it may be the climate’s indirect influences of factors such as food production, water supply and habitat - Biological aspects (competition) * Why might species not be evenly distributed (e.g. with respect to density over their range) * How can the distribution of individuals in a population give some indication of their interactions? - Not evenly distributed - SMALL SCALE (small distances with little environmental change) - Distribution may be random, regular, or clumped - Produced by interactions between individuals within a population, by structure of the physical environment, or by a combination of interactions and environmental structure - Individuals within a population may attract each other, repel each other, or ignore each other - Mutual attraction creates clumped patterns of distribution - Avoidance or claiming of exclusive use of landscape produces regular distribution - Neutral responses create random distributions - These are “social interactions” - LARGE SCALE - Distributions are clumped around favorable environmental conditions - “Hot spots” * How could you test what factors affected distributions? - Hold all factors constant except for the one you’re trying to test, if there is a change then it did affect it - Hold resources constant and manipulate distribution - May also test interactions between these factors * What is the relationship between body size and population density? - Population density declines with increasing organism size - (-3/2) ratio - Plants are similar except they vary more within a particular species in terms of their size - Reasons: Resource requirement per individual, ability to find mates, proportional biomass
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* For a given body size, why do aquatic invertebrates generally have higher densities than terrestrial vertebrates? - Water is three-dimensional…one km² of water can potentially hold a lot more fish than one km² of land can hold terrestrial animals LECTURE 8 – POPULATION DISTRIBUTIONS AND ABUNDANCE * What are the four main sources of change in population sizes? - Natality, mortality, immigration, emigration Cohort – A group born at the same time Cohort life table – Shows data of the group Static life table – Record the age at death of a large number of individuals… individuals are born at different times…”static” because method involves a snapshot of survival within a population during a short interval of time Survivorship curve – Plots number of survivors per 1,000 births against age…shows patterns of life and death within a population * What life history characteristics are associated with the different types of survivorship curves? - Type 1: A relatively high rate of survival among young and middle-aged
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EcologyTest2Studying - LECTURE 7 POPULATION DISTRIBUTIONS...

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