3.1 Community Ecology • A biological community is a group of interacting populations that occupy the same area at the same time
Communities • Organisms rely on one another to survive • Abiotic factors affect communities and the organisms in them • Organisms adapt to the conditions they live in • Cactus retaining water in the harsh climate of a desert • Depending on which factors are present, organisms can survive in one ecosystem, but not others
Limiting Factors • Any abiotic or biotic factor that limits the numbers, reproduction, or distribution of organisms • Includes sunlight, temperature, climate, water, nutrients, fire, soil chemistry, space, and other living things • How would temperature be a limiting factor for polar bears?
Range of Tolerance • The upper and lower limits that define the conditions in which an organism can survive • Ideal water temp for steelhead trout is between 9°C and 25°C • The ability of an organism to survive in certain abiotic or biotic factors is called tolerance
Ecological Succession • The living and nonliving parts of an ecosystem change over a period of time • Forest fire • The changes that take place in a community as it gets older is called SUCCESSION
Succession Succession happens SLOWLY! So it can be hard to see happening.
Primary Succession • occurs at an area of NEWLY EXPOSED rock (no soil) that has never been occupied by any living things (biotic factors)
Pioneer Species • Lichens – a combination of fungus and algae • Lichens begin to grow on the bare rock • Since they are the first organisms to appear, they are called pioneer species • Pioneer species help to create soil by secreting acids that break down the rock
Climax Communities • A mature community eventually develops from bare rock • Climax Community – the stable, mature community that results when there is little change in the composition of species • It is the final stage of succession in a community, however, because of ecological disturbances, climax communities are unlikely to occur
Secondary Succession • Occurs when a community has been removed due to fire, flood, windstorm, etc. • New species may begin to occupy the habitat • Over time, the species belonging to the mature community may return
Secondary Succession • The orderly and predictable change that takes place after a community of organisms has been removed, but the soil has remained intact.
4.1 Population Dynamics • Populations of species are described by density, spatial distribution, and growth rate • Population Density – the number of organisms per unit area
Spatial Distribution • Dispersion – the pattern of spacing of a population within an area • Uniform, clumped groups, or random • One primary factor in the pattern is availability of resources
Population Range • No population, not even humans, occupies all habitats in the biosphere • A species may not be able to expand it population range because it cannot survive the abiotic or biotic conditions found in the expanded range • Abiotic conditions – temperature, rainfall, sunlight, humidity level • Biotic conditions – predators, competitors, parasites
Population Limiting Factors • Factors that keep a population from continuing to increase • Density-independent • Density-dependent
Population Limiting Factors Density-Independent Density-Dependent any factor that depends on the number of members in a population Usually biotic Competition – density is high, resources are low Disease – density is high Parasites – density is high • any factor that does not depend on the number of members in the population • Usually abiotic • natural events like the weather (drought, flooding, etc.) • human interference
Population Growth Rate • Explains how fast a given population grows • Emigration – number of individuals moving away from a population • Immigration – number of individuals moving into a population • Most populations remain the same size from year to year
Population Growth Rate • A population stops increasing when the number of births is less than the number of deaths, or when emigration (moving out) exceeds immigration (moving in)
Carrying Capacity • Maximum number of species an environment can support for the long term • Limited by energy, water, oxygen,
Reproductive Patterns • Species of organisms vary in the number of births per reproduction cycle, the age that reproduction begins, and in the life span of the organisms • Plants and animals are placed into groups based on their reproductive factors • R-strategists • K-strategists
Reproductive Patterns R-Strategists K-Strategists Carrying-capacity Live in environments that are predictable Larger organisms (elephant) Long life span, produce few offspring Controlled by density-dependent factors STRATEGY: produce fewer offspring that have a better chance of living • Rate strategy • Live in an environment that fluctuate • Usually small organisms (mice, fruit fly) • Short life spans, produce many offspring • Usually controlled by density-independent factors • STRATEGY: produce as many offspring as possible in a short period of time
4.2 Human Population • Demography: the study of human population size, density, distribution, movement, and birth and death rates
Advances • For years, environmental conditions kept the human population size below carrying capacity • Humans have altered the environment to change the carrying capacity
Advances • Agricultural advances • Domestication of animals • Technology • Medicine • Improvements in shelter
Human Population Growth Rate • Although the population is still growing, the growth rate has slowed
Trends in Human Population Growth • Can be altered by war and disease • Demographic Transition – change in population from high birth/death rates to low birth/death rates
Zero Population Growth • (ZPG) when births plus immigration = deaths plus emigration • The population has stopped growing because births and deaths occur at the same rate
Human Carrying Capacity • Scientists are concerned about the population reaching or exceeding the carrying capacity • Resources from the biosphere used by each person must also be limited
Population Ecology Chapter 4 Chapter Diagnostic Questions CDQ 1 What term is used to describe the number ofindividuals moving into a population? • A • B • C • D • emigration • imitation • immigration • migration
Population Ecology Chapter 4 Chapter Diagnostic Questions CDQ 2 What is population density? • A • B • C • D • pattern of spacing of a population in an area • number of organisms in an area • characteristics of a population • manner in which a population grows
Population Ecology Chapter 4 Chapter Diagnostic Questions CDQ 3 When does zero population growth occur? • A • B • C • D • when birth rate equals death rate • when death rate exceeds birth rate • when birth rate exceeds death rate • when there are zero births
Population Ecology Chapter 4 4.1 Formative Questions FQ 1 Which is a density-dependent factor? • A • B • C • D • disease • fire • flooding • weather
Population Ecology Chapter 4 4.1 Formative Questions FQ 2 Which is a density-independent factor? • A • B • C • D • competition • extreme cold • parasites • predation
Population Ecology Chapter 4 4.1 Formative Questions FQ 3 Which factor can limit the carrying capacity of a population? • A • B • C • D • emigration • predation • available nutrients • extreme temperatures
Population Ecology Chapter 4 4.2 Formative Questions FQ 4 The study of the size, density, distribution, and movement of the human population is _______. • A • B • C • D • bioinformatics • demography • ecology • ethnography
Population Ecology • decreased agriculture • famine and wars • setbacks in medicine • voluntary population control Chapter 4 4.2 Formative Questions FQ 5 Which is a primary reason for the decline in the percent growth of the human population after 1962? • A • B • C • D
Population Ecology Chapter 4 4.2 Formative Questions FQ 6 What will happen to the human population when the birthrate equals the death rate? • A • B • C • D • CDC • HPG • PGR • ZPG
Population Ecology Chapter 4 Chapter Assessment Questions CAQ 1 Which type of population growth model does this graph represent? • A • B • C • D • exponential • spatial • genetic • logistic
Population Ecology Chapter 4 Chapter Assessment Questions CAQ 2 Based on the information in the graph, infer which statement accurately represents the information provided. • A • B • C • D • India has very little land for farming. • Germany is smaller per acre than the United States. • More land is used to support an individual in the United States. • A person in Indonesia requires more land than a person in Brazil.
Population Ecology Chapter 4 CAQ 3 Chapter Assessment Questions Use the graph to explain the growth of the mice population.
Answer: If two adult mice breed and produce a litter and their offspring survive to breed, then the population grows slowly at first. This slow growth is defined as the lag phase. The rate of population growth begins to increase rapidly because the total number of organisms that are able to reproduce has increased. Exponential growth occurs when the growth rate is proportional to the size of the population. All populations grow exponentially until some limiting factor slows the population’s growth. Population Ecology Chapter 4 CAQ 4 Chapter Assessment Questions
Population Ecology Chapter 4 Standardized Test Practice STP 1 An ecologist estimates a population density of 2.3 lemmings per square meter of tundra. What would be the approximate number of lemmings over 1000 square meters of tundra? • A • B • C • D • 0.23 • 23 • 230 • 2300
Population Ecology Chapter 4 Standardized Test Practice STP 2 The ecologist finds that over a 1000m2 plot of tundra, lemmings tend to concentrate in clumps in drier areas. What is the term for this pattern of spacing? • A • B • C • D • density • dispersion • logistic spacing • spatial distribution
Population Ecology Chapter 4 Standardized Test Practice STP 3 Brine shrimp are able to survive only in certain lakes that have a very high salt concentration. Which is the correct population characteristic of brine shrimp? • A • B • C • D • It is density-dependent. • It is limited by biotic factors. • It has a limited spatial distribution. • It is randomly dispersed in the environment.
Population Ecology Chapter 4 Standardized Test Practice STP 4 Why does the population growth level off at 10,000? • A • B • C • D • Biotic factors have made survival difficult. • The population has reached its carrying capacity. • Density-independent factors have slowed the growth of the population. • Immigration into the population has reached the maximum limit.
Population Ecology Chapter 4 Standardized Test Practice STP 5 Which organism is the best example of a k-strategist? • A • B • C • D • wolf • grasshopper • rabbit • whale
Population Ecology Chapter 4 Glencoe Biology Transparencies
Population Ecology Chapter 4 Image Bank