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Chapters 5&6 – Populations and Human Growth
Section 5-1: How Populations Grow
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3 important characteristics of a population are its
geographic distribution, density, and growth rate
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Geographic distribution
______________________ is just the area inhabited by the population __________________ is the number of individuals per unit area Population density Growth rate depends on several factors; number of _______, number of ______, and the number of ________________ ____________________________ births deaths individuals that enter or leave the population
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A population _______ if more individuals are born than the number that dies (_____________________)
If birthrate ___ death rate, then the population _________ __________ A population _______ if more individual die than are born (_____________________) grows birthrate >death rate = stays the same size shrinks death rate >birthrate
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_____________ = when individuals move into an area
____________ = when individuals move out of an area Immigration Emigration Immigration Emigration
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There are several different models of population growth;
exponential and logistic Logistic growth Exponential growth
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Exponential growth occurs when the individuals in a population
Needs ________________ & ___________________ reproduce at a constant rate ideal conditions unlimited resources
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We end up with a _______ curve, just continues to go up
J-shape Exponential growth doesn’t happen in natural populations for very long
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Logistic growth occurs when
This happens because _________________________________, the growth of a population slows or stops a population’s growth slows or stops following a period of exponential growth as resources become less available
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We end up with an ________ curve – things level off
S-shape Birthrate, death rate, immigration, and emigration can all have an impact of why a populations growth levels off
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Even when population growth “stops”, it still ____________, but averages out around a certain point
varies a little __________________ = the point where growth evens out – it is the ______________ of individuals that a given environment can support Carrying capacity largest number
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Section 5-2: Limits to Growth
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There are different types of factors that affect the growth of a population
Limiting factor ______________ = a factor that causes population growth to decrease A ____________________ can also affect the long-term survival of a species as well as population growth limited resource base
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________________________________ = a limiting factor that depends on population size
Density-dependent limiting factor These factors are only limiting when the population density reaches a certain level
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They are more prevalent in large, dense populations
They include competition, predation, parasitism, and disease
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Competition can occur between members of the ______ species or even members of _________ species
same different The more individuals in an area, the _______________________________, the more competition there is sooner they use up the resources 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
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The regulation of a population by predation takes place within the ___________________________, its just one big cycle! predatory-prey relationship
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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
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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 in its path, it doesn’t matter what size it is Human activities, like housing developments, will also affect anything in its path
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Human Population Growth
Section 5-3: Human Population Growth
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Demography _____________ = the scientific study of human populations The goal of demography is to _______________________ of human populations and figure out how populations examine characteristics Birthrates, death rates, and age structure help us predict why some countries have high growth rates and some don’t will change over time
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Population growth also depends on the age of people within the population
An ______________________ shows the population of a country broken down by age and gender These diagrams can help predict age-structure diagram future growth rates
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Ex. If there are equal numbers of individuals in the different age groups, it predicts slow and steady growth Ex. If there are many more children and teenagers, this predicts rapid growth
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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
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Section6-1: A Changing Landscape
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Humans have a vast effect on any ecosystem they become part of
Humans use ________ energy and transport ________ materials as _________________________ combined as much as many all other multicellular species Some important activities that affect the biosphere are hunting and gathering, __________, industry and agriculture urban development
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Even with the advances in agriculture, there still ended up being _____________ in many parts of the world food shortages Science met this shortage with an answer _______________ = the development of highly productive crop strains and the use of modern agricultural techniques to increase yields of food crops Green revolution The green revolution has helped many people greatly and has even helped world food production double
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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 _________ insects, ___________ water supply and accumulate in the environment Water for irrigation is limited and may run dry beneficial contaminate
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Renewable and Nonrenewable Resources
Section 6-2: Renewable and Nonrenewable Resources
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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
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__________________ = a resource that can regenerate if alive or can be replenished by biogeochemical cycles if nonliving They are not necessarily Renewable resource unlimited _____________________ = a resource that cannot be replenished by natural processes Ex. Nonrenewable resource Fossil fuels The classification of a resource depends on its context
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Sustainable development
______________________ = a way of using natural resources without depleting them and providing for humans needs without causing long-term environmental harm
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_____ is an important resource – it provides space, raw materials for industry, and soil to grow crops in Land Food crops grow best in ______ soil this can be maintained through interactions between the soil and the plants growing in it fertile
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_______ are also important resources – they provide us with fuel, _____________, and produce oxygen
The type of forest determines whether it is renewable or nonrenewable Forests create habitats Deforestation = loss of forests
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_______ and the organisms that live in them are a valuable food resource
Oceans Fishing _______ is considered a __________ resource – the fish can reproduce – but overfishing threatens to harm the resource ___________ = the raising of aquatic animals for human consumption this has helped to sustain the resource renewable ___ is a resource we use all the time and rarely think about Air Aquaculture
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___________ is a __________ resource, but the total supply is limited
Natural habitats like _________ can help to purify and maintain our water supply Freshwater renewable wetlands
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Section 6-3: Biodiversity
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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
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__________ is considered to be our greatest natural resource and can provide us with many things
Biodiversity _________ = when a species disappears from all or part of its range Humans have hunted a number of animals into Extinction extinction
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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”
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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 ______________ and organisms could not eliminate it from their body. The higher up the food chain, the more DDT was found in organisms. nondegradable _____________________ = concentrations of harmful substances increase in organisms at higher trophic levels Biological magnification
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______________ = 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 Invasive species native species
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Hot spots ________ are being identified around the world to help us zone in on where organisms are in danger
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