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Section 5-1: How Populations Grow 3 important characteristics of a population are its geographic distribution, density, and growth rate Geographic distribution is just the area inhabited by the ______________________ population __________________ Population density is the number of individuals per unit area Growth rate depends on several factors; number of births number of deaths _______, ______, and the number of ________________ individuals that ____________________________ enter or leave the population grows if more individuals are born than the A population _______ number that dies (_____________________) birthrate >death rate If birthrate ___ stays the = death rate, then the population _________ same size __________ A population _______ shrinks if more individual die than are born death rate >birthrate (_____________________) Immigration = when individuals move into an area _____________ Emigration = when individuals move out of an area ____________ Immigration Emigration There are several different models of population growth; exponential and logistic Logistic growth Exponential growth Exponential growth occurs when the individuals in a population reproduce at a constant rate Needs ________________ ideal conditions & ___________________ unlimited resources J-shape curve, just continues to go up We end up with a _______ Exponential growth doesn’t happen in natural populations for very long Logistic growth occurs when a population’s growth slows or stops following a period of exponential growth This happens because _________________________________, as resources become less available the growth of a population slows or stops We end up with an S-shape ________ curve – things level off Birthrate, death rate, immigration, and emigration can all have an impact of why a populations growth levels off varies a little Even when population growth “stops”, it still ____________, but averages out around a certain point Carrying capacity = the point __________________ where growth evens out – it is the largest number of individuals that ______________ a given environment can support There are different types of factors that affect the growth of a population Limiting factor = a factor that causes ______________ population growth to decrease A limited ____________________ resource base can also affect the long-term survival of a species as well as population growth Density-dependent limiting factor = a limiting ________________________________ factor that depends on population size These factors are only limiting when the population density reaches a certain level They are more prevalent in large, dense populations They include competition, predation, parasitism, and disease Competition can occur between members of the ______ species or even members of _________ same different species The more individuals in an area, the _______________________________, sooner they use up the resources the more competition there is Competition between species helps drive evolution when the 2 species are competing for the same resource, there is pressure to change to decrease the competition The regulation of a population by predation takes place within the predatory-prey relationship its ___________________________, just one big cycle! Density-independent limiting factor = a __________________________________ limiting factor that affects all populations in similar ways, regardless of population size They include unusual weather, natural disasters, seasonal cycles, and certain human activities The Midwest has experienced an unusually hot summer this year the hot weather has affected many populations in different locations, regardless of the size A large storm, like hurricane Katrina, will affect anything Human activities, like housing in its path, it doesn’t matter developments, will also affect what size it is anything in its path Section 5-3: Human Population Growth Demography _____________ = the scientific study of human populations The goal of demography is to _______________________ examine characteristics of Birthrates, death rates, and human populations and age structure help us predict figure out how populations why some countries have high will change over time growth rates and some don’t Population growth also depends on the age of people within the population An ______________________ age-structure diagram shows the population of a country broken down by age and gender These diagrams can help predict future growth rates Ex. If there are equal numbers Ex. If there are many more of individuals in the different children and teenagers, this age groups, it predicts slow predicts rapid growth and steady growth Will humans ever reach their carrying capacity? Statistics show that the human population is still growing, but not as fast as it once was A lot of ecologists say that if human growth doesn’t slow more than it has, there could be serious damage to the, environment Humans have a vast effect on any ecosystem they become part of Humans use ________ as much energy and transport ________ as many materials as _________________________ all other multicellular species Some important activities combined that affect the biosphere are hunting and gathering, __________, industry and agriculture urban development Even with the advances in agriculture, there still ended up being food _____________ shortages in many parts of the world Science met this shortage with an answer Green revolution = the development of _______________ highly productive crop strains and the use of modern agricultural techniques to increase yields of food crops The green revolution has helped many people greatly and has even helped world food production double With increased food supply came ecological challenges Monoculture can lead to insect issues if they have a large supply of food, their population can grow rapidly Pesticides can kill _________ beneficial insects, ___________ contaminate water supply and accumulate in the environment Water for irrigation is limited and may run dry Humans use many resources on a daily basis and we need to remember to protect these resources Environmental goods and services may be classified as either renewable or nonrenewable Renewable resource = a resource that can regenerate if __________________ alive or can be replenished by biogeochemical cycles if nonliving They are not necessarily unlimited Nonrenewable resource = a resource that _____________________ cannot be replenished by natural processes Ex. Fossil fuels The classification of a resource depends on its context ______________________ Sustainable development = a way of using natural resources without depleting them and providing for humans needs without causing long-term environmental harm Land _____ is an important resource – it provides space, raw materials for industry, and soil to grow crops in fertile soil Food crops grow best in ______ this can be maintained through interactions between the soil and the plants growing in it Forests _______ are also important resources – they provide us with fuel, _____________, create habitats and produce oxygen The type of forest determines whether it is renewable or nonrenewable Deforestation = loss of forests Oceans and the organisms that live in _______ them are a valuable food resource _______ is considered a Fishing __________ resource – the fish renewable Air is a resource we use ___ can reproduce – but overfishing all the time and rarely threatens to harm the resource think about ___________ Aquaculture = the raising of aquatic animals for human consumption this has helped to sustain the resource Freshwater is a __________ renewable resource, but ___________ the total supply is limited Natural habitats like _________ wetlands can help to purify and maintain our water supply Since humans are part of global food webs, we are closely tied to the well-being of other organisms Biodiversity the sum total of ___________= the genetically based variety of all organisms in the biosphere Biodiversity __________ is considered to be our greatest natural resource and can provide us with many things Extinction = when a species _________ disappears from all or part of its range Humans have hunted a number of animals into extinction Endangered species = a species whose population size is _________________ shrinking and are in danger of becoming extinct ___________________ Habitat fragmentation = when an ecosystem is split up into smaller pieces or “islands” Different pollutants can be very hazardous to local ecosystems and can harm organisms all along the food chain Ex. DDT was a pesticide used. It was ______________ nondegradable and organisms could not eliminate it from their body. The higher up the food chain, the more DDT was found in organisms. Biological magnification = _____________________ concentrations of harmful substances increase in organisms at higher trophic levels ______________ Invasive species = species that are non-native and introduced to new habitats Because they have no natural predators, the population can grow rapidly and they have an adverse effect on native species ________ Hot spots are being identified around the world to help us zone in on where organisms are in danger