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Objective Explain how population sizes are regulated. Key Terms Population Dispersion Growth rate Reproductive potential Carrying capacity What Is a Population? Group of organisms of the same species live in the same area interbreed Organisms usually breed with members of their own population. Populations “Population” refers to the group as a whole or the size - number of individuals (members) in the group. Populations Population Density - number of members that live in a specific area. Populations Dispersion distribution of organisms in a population Clumped Uniform Random Growth Rate Population change over time can be represented by: Growth Rate Changes when birth rates and death rates increase or decrease. Can be positive, negative, or zero. Growth Rate Positive – average number of births > average number of deaths Negative - average number of births < average number of deaths Zero - average number of births = average number of deaths Growth Rate Population sizes usually stay the same Certain factors control the sizes of populations (limiting factors). • • • • space disease immigration/emigration predators and parasites Reproductive Potential The maximum number of offspring a specific organism can produce. Depends upon fecundity fertility gestation Reproductive Potential Increases when individuals produce more offspring at a time reproduce more often reproduce earlier in life • shortens generation time – average age of reproduction Reproductive Potential Small times organisms have short generation can reproduce after few hours/few days populations grow quickly Reproductive Potential Large organisms reach reproductive age after years have a much lower reproductive potential populations grow slowly Exponential Growth A large number of individuals is added to the population each generation. Numbers increase by a certain factor (usu. 2). Occurs in nature with plenty of resources and no predators. Limits to Population Growth Only the best adapted members of a population will survive and reproduce. Characteristics of a population may evolve over time. Carrying Capacity Largest population an environment can support at any time. Population can increase beyond this number but cannot stay elevated Carrying Capacity Estimated by average population sizes or by observing population crashes after a certain size has been exceeded. Resource Limits Resource Limits Carrying capacity is reached when species consume a resource at the same rate that the resource is produced. resource consumption = resource creation That natural resource is called a limiting resource. Food Water Light Competition Within a Population Resource competition increases as population approaches carrying capacity. Competition within a population is part of the pressure of natural selection. Competition Within a Population Members of a species may compete indirectly for social dominance or for a territory. A territory is an area defended by one or more individuals against other individuals. space shelter food mates breeding sites Population Regulation Causes of death in a population may be density dependent or density independent. Population Regulation Density dependent cause of death deaths occur more quickly in a crowded population than in a sparse population. Limiting factors Predation Emigration Population Regulation Population Regulation Density independent cause of death – some of the population can die regardless of the population’s density. Severe weather Natural disasters Do Now/Objective – separate paper…Hand In (4 min) Do all living organisms interact in the same way? List the different ways organisms interact with each other. Niche Ecological A role of an organism where it makes its home resources it needs to survive how it interacts with other organisms niche includes an organism’s habitat. habitat is an area within an ecosystem. Niche Map All organisms use their habitats in a unique way. Think about your niche (where you fit into your community) and answer: • Where do you gather your favorite resources? • Who do you compete or cooperate with? • Where do you live and where do you hang out? • Do you spend certain parts of the day in certain places? Draw a niche bubble map that shows how your use your habitat. INCLUDE 4+ interactions and describe those interactions on your maps. Key Terms Niche Competition Predation Parasitism Mutualism Comensalism Symbiosis Species Interaction Five • • • • • main types of interactions: Competition Predation Parasitism Mutualism Commensalism Competition Organisms try to use the same limited resource Members of the same species compete they require the same resources they occupy the same niche Indirect Competition Species can compete even if they never come into direct contact with each other. Adaptations to Competition Members of different species sometimes compete (niche overlap) each species use some of the same resources in a habitat. Adaptations to Competition Law of Competitive Exclusion No two species can occupy the same niche (competing for the same resources) at the same time indefinitely Adaptations to Competition The niche species will often divide up the by area by time of use Adaptations to Competition Niche restriction - each species uses less of the niche than they are capable of using. Actual niche may be smaller than potential niche. Adaptations to Competition Predation One species kills and eats the other species predator prey Predators Some predators eat only specific types of prey. sizes of both populations have a direct relationship Parasitism An organism lives in or on another organism to feed on the other organism parasite host Parasitism vs. Predation Parasites depend on their hosts; usually don’t kill them. The host is often weakened or diseased by the parasite. Symbiosis Relationship where two different organisms benefit from each other Mutualism Commensalism Mutualism Relationship between two species where both species benefit. Commensalism Relationship between two organisms where one organism benefits and the other is unaffected. Coevolution Can occur with species in symbiotic relationships. species may evolve adaptations that improve the benefits to each member. Species Interactions Interaction Type 1. 2. 3. 4. 5. Competition Species A Species B (harmed or (harmed or benefited) benefited) Harmed Harmed Description Your own example Both parties struggle for a limited resource Coyote and kit fox both hunting kangaroo rat