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Transcript
Unit 6 Populations Dynamics Define these 26 terms: • • • • • • • • • Commensalism Habitat Herbivory Mutualism Niche Parasitism Predator Prey Resource Partitioning • Symbiosis • Age structure • Population density • Population distribution • Population size • Sex ratio • Carrying capacity • Emigration • Immigration • Migration • Age structure diagram • Population • Biotic potential • Density dependent factor • Survivorship curve • Invasive species • Succession Population Dynamics Species Interactions Unit 6A Chp. 5.2 REVIEW Ecosystems: Everything is Connected What is an ecosystem? An ecosystem includes all the different organisms living in a certain area, along with their physical environment Two parts of an ecosystem: Biotic Factors: The living parts of an ecosystem which interact with each other and the nonliving parts Abiotic Factors: The nonliving parts of the ecosystem Hierarchy • Biosphere • Ecosystem • Community • Population • Species • Organism Niche v.s. Habitat……… • Niche: • all of the organism’s relationships with its environment (both living and nonliving), a way of life • Examples: what it eats, what its parasites are, rotting when it dies, when & how it reproduces, biorhythms, … • Habitat: • The actual place an organism lives • Examples: rain forest, freshwater pond, coral reef,… Tolerance & Competition • Tolerance – ability to survive and reproduce under changing environmental conditions – Specialists – very restricted tolerance ranges • Competition – when multiple organisms seek the same limited resources Competitive Exclusion • When a competitor species is very effective and excludes another species from the resource use entirely. – Example: the invasive species zebra mussels outcompeted 20 native mussels in Lake St. Clair by 1997. Resource Partitioning • When competing species partition or divide the resource they use in common by specializing in different ways • Ex. – birds specialize by particular types of insects & parts of the tree ; can lead to evolution - Galapagos Is. SYMBIOSIS A long-term and physically close relationship between two organisms from different species in which at least one organism benefits. Ways species interact with each other: • Predation • Competition • Parasitism • Mutualism • Commensalism Predation 1. Predation – one organism kills and eats another organism 2. Prey – the organism that is eaten 3. Predator – the organism that does the eating 4. Example: lynx and hare Competition: A relationship between species in which they attempt to use the same limited resource Can be direct or indirect Parasitism 1. Parasite – organisms that live in or on another organism and feed on it without immediately killing it 2. Host – the organism the parasite takes its nourishment from 3. Parasitism – the relationship between parasite & its host Mutualism • A cooperative partnership between two species • Both benefit • Examples? • Barn cat and farmer • Sea Anemone and Anemonefish Commensalism • A relationship in which one species benefits and the other is neither harmed nor helped • Example? • Bromeliad and tree • Shark and ramoras Herbivory • The interaction when an animal feeds on a plant • Most common type: insects • In most cases, herbivory does not kill a plant directly but it may affect its growth and reproduction • Plant defenses: toxic chemicals, thorns, spines, irritating hairs, hormones that stimulate growth Unit 6A (5.2) Review 1. Explain how competition can affect an organism’s niche. 2. How are predation, parasitism, & herbivory similar? Different? 3. Human digestive tract is filled with bacteria that get nutrients by helping digest food. Is this symbiotic? Mutualism or commensalism? Explain. • When finished with this small group work, quietly work on your vocabulary Population Dynamics Unit 6B Describing Populations Chp. 4.2 Population Size • The # of individual organisms present in a given population at a given time • May increase, decrease, undergo cyclical change or remain the same over time (healthy pop.) • If a population declines rapidly, it can mean extinction is coming (ex. Passenger pigeon) Determining Population Size • In almost all cases, population size is estimated using sampling techniques. – Ecologists count the # in a smaller sample area, then estimate the # in the larger overall area – Sometimes it is easier to find signs of organisms instead of the organisms themselves Population Density • # of individuals within a population per unit area • Higher population densities make it easier to find mates or group together, however crowding leads to parasites and competition Population Distribution • Describes how organisms are arranged within an area • Random distribution – individuals arranged in no particular pattern • Uniform distribution – organisms are spread evenly in an area • Clumped distribution – individuals arrange themselves based on availability of resources Age Structure & Sex Ratios • # of organisms of each age within a population • Age structure diagrams – tools scientists use to show the age structure of populations • Sex ratio – proportion of males to females 4.2 Review • How is a population’s size related to its well-being? • Which population of flamingos is more dense: 15 flamingos in a 5-square-meter area, or 40 flamingos in a 10-squaremeter area? • Describe the 3 patterns of population distribution. Which of these is the most common distribution in nature? • 4.2 review packet Population Dynamics Unit 6C Population Growth Chp. 4.3 Factors that determine Population Growth • Births, deaths, immigration, emigration • Natality – rate of birth • Mortality – rate of death • Survivorship curve – shows how likelihood of death varies with age, Types I, II, & III • Type I – individuals are most likely to die when they are old • Type II – mortality remains constant throughout an individual’s lifetime • Type III – mortality is highest for young members of the population Migration • Seasonal movement into or out of an area • Immigration – arrival of individuals from outside a given area • Emigration – departure of individuals from a given area • Births & immigrations add individuals to a population; deaths & emigrations subtract Calculating Population Growth individuals added – individuals subtracted • Tells us net change in population size • Ex. – annual birthrate = 18/1000, annual death rate = 10/1000, annual immigration rate = 5/1000, annual emigration rate = 7/1000. Calculate annual growth rate • (18 + 5) – (10 + 7) = 6 • Usually expressed as a percent • (6/1000) x 100% = 0.006 x 100% = 0.6% How Populations Grow • Exponential Growth – when a population increases by a fixed % each year, J curve • Logistic Growth – describes how a population’s exponential growth is slowed and finally stopped by limiting factors which determine its ultimate carrying capacity • In nature, usually populations fluctuate or rise & crash Limiting Factors • Density-dependent factors – high population density increase competition for resources; ex. – predation, disease, food & water • Density-independent factors – limiting factors whose influence is not affected by pop. density; ex. – floods, fires, landslides, climate change Biotic Potential • The maximum ability of an organism to produce offspring in ideal conditions • Influenced by gestation time (embryo to birth) and generation time (birth to sexual maturity), as well as # of offspring born at a time 4.3 Review • A population has a birthrate of 10/1000, a death rate of 9/1000, an immigration rate of 3/1000, and an emigration rate of 7/1000. What is its growth rate? Is the population getting larger or smaller? • What is the difference between exponential growth & logistic growth? Which is more common over long terms in nature? • In your own words, define limiting factor and biotic potential. • 4.3 review packet Population Dynamics Unit 6D Community Stability Chp. 5.4 Ecological Succession • Somewhat predictable series of changes over time experienced by a community • Primary succession – when a disturbance is so severe, no vegetation or soil life remains • Secondary succession – begins when a disturbance dramatically alters an existing community but does not destroy all living things • Pioneer species – colonize newly exposed land first in primary succession; ex. – lichen take firm hold on rock, capture moisture, release acids, soil begins to form • Climax community – a stable community that “completes” the succession process; ex. – beech-maple forests, old growth forests Invasive Species • Non-native organisms that spread widely in a community because they lack limiting factors • Not all exotic species become invasive as some stay small & localized • Not all invasive species are bad, ex. – European honeybee • Bad ex’s – zebra mussels, cane toad, kudzu vine 5.4 Review • Explain how disturbances can throw a community out of a balanced state and into a period of adjustment. • List examples of primary & secondary succession and describe the stages; identify the factors that determine the type of succession that will occur. • Identify a pioneer species & list several examples in different ecosystems. • Describe the how, when, where of climax communities. • List examples of invasive species in Florida.