Ecology Unit AP Biology Chapter 53 Population Ecology

Ecology Unit AP Biology

Chapter 53: Population Ecology � Populations are groups of individuals of the same species that live in the space ◦ Greater diversity within a population promotes greater survival chances for the population � Three aspects of populations are especially important: ◦ the range in which a population occurs ◦ the pattern of spacing of individuals throughout their range ◦ the size a population eventually attains

Factors Affecting Population Growth � Sex Ratio ◦ the number of births is directly related to the number of females � Generation Time ◦ Interval between the birth of an organism and the birth of its offspring �Shorter generation times result in faster growth � Age Structure ◦ The relative number of individuals in each age range �A large proportion of young individuals results in faster growth �More individuals will be reproducing in time �A large proportion of older individuals results in slower growth �Fewer individuals will reproduce �Most reproduction occurred in past

Survivorship Curves � Type I ◦ Organisms with long life spans, long generation times ◦ Most live to full life expectancy � Type II ◦ Organisms with moderate life spans ◦ Equal chances of living to full life expectancy � Type III ◦ Organisms with short life spans ◦ Most die before reaching ¼ of life span ◦ Short generation times

Carrying Capacity is determined by the Effect of Limiting Factors Density Dependent � Factors whose effect is realized as population size increases ◦ ◦ Competition Disease Predation Resource availability Density-Independent � Factors whose effect is realized regardless of population size ◦ Drought ◦ Storms ◦ Seasonal extremes

Population Growth Models Exponential Growth Logistic Growth � Growth without constraints � No limit to growth � Biotic potential is realized ◦ Maximum rate at which a population size increases without limits � Rate increases logarithmically is limited by various factors � Population stabilizes � Carrying capacity is reached ◦ Maximum number of individuals supported by the environment

Reproductive Strategies K-Selected Species � Long Life spans � Long generation times � Fewer offspring per reproductive event � Multiple reproductive events per life cycle � Parental care � Greater chance of survival (Type I) � Long maturation time r-Selected Species � Short life span � Short generation time � Many offspring per reproductive event � One reproductive event per life cycle � Little parental care � Low survival chances (Type III) � Short maturation time

Population Growth: Key Points � Reproduction without constraints results in the exponential growth of a population. �A population can produce a density of individuals that exceeds the system’s resource availability. � As limits to growth due to density-dependent and density independent factors are imposed, a logistic growth model generally ensues

Chapter 54: Community Ecology � Communities are composed of populations of organisms that interact in complex ways. � The structure of a community is measured and described in terms of species composition and species diversity � A niche is the role an organism plays in the habitat in which it lives. � When two organisms occupy the same niche competition occurs ◦ Competitive Exclusion �When two species attempt to occupy the same niche one species is eliminated due to competition

Competitive Exclusion Principle

Symbiosis INTERACTION Competition Predation Parasitism Mutualism Commensalism CHARACTERISTICS ONE (1) EXAMPLE

Factors Influencing Communities and Populations � Competition, parasitism, predation, mutualism and commensalism can affect population dynamics. � Relationships among interacting populations can be characterized by positive and negative effects � Many complex symbiotic relationships exist in an ecosystem, and feedback control systems play a role in the functioning of these ecosystems.

Competition in Communities INTERspecfic � Between competing species � Resources include ◦ Food ◦ Range ◦ Habitat INTRAspecific � Between members of one species � Within a species � Resources include ◦ ◦ Food Range Habitat MATES

Predator-Prey Interactions � Cyclical nature of populations � Predator growth follows prey growth � Predators limit prey population � Availability of prey limits predator population

Keystone Species � The effects of keystone species on the ecosystem are disproportionate relative to their abundance in the ecosystem, and when they are removed from the ecosystem, the ecosystem often collapses. � Examples include: ◦ ◦ Predators Prey Producers Decomposers

Succession Primary Succession � Occurs on new land � No previous plant life present ◦ Pioneers are moss, lichens � Requires long time period to reach climax community Secondary Succession � Occurs on land that had previous plant growth ◦ The result of land being cleared by humans or natural events � Requires less time to reach climax community

Primary Succession

Secondary Succession

Chapter 55: Ecosystems � Ecosystems consist of communities interaction with each other and the environment � The stability of populations, communities and ecosystems is affected by interactions with biotic and abiotic factors � A cycling of abiotic factors occurs within an ecosystem ◦ These include water, nitrogen, carbon, and phopshorous � Interactions among living systems and with their environment result in the movement of matter and energy. ◦ Energy flows, but matter is recycled

Nutrient Recycling: Nitrogen Cycle � Bacteria (decomposers) function to recycle matter � Nitrogen is recycled by the following bacteria: ◦ Nitrogen Fixing Bacteria �Convert atmospheric nitrogen into nitrates �Nitrates are useable by plants to produce amino acids �Symbiotic relationship with plants – live in root nodes ◦ Denitrifying Bacteria �Convert nitrates into nitrogen (N 2) gas ◦ Ammonification Bacteria �Convert urea and uric acid (wastes) into ammonia ◦ Nitrifying bacteria �Convert Ammonia into nitrite and nitrate

Water Cycling � Water continuously cycles between the bodies of water, land, organisms, and atmosphere. � More than 96% of all fresh water in the United States is groundwater. � An estimated 2% of the groundwater in the Untied States is already polluted. � Cutting down forests disrupts the water cycle as lower amounts of moisture are returned to the atmosphere.

Carbon Cycling � About 10% of the carbon dioxide in the atmosphere is fixed annually by photosynthesis. � When the bodies of dead organisms decompose, microorganisms release carbon dioxide into the atmosphere, freeing it for incorporation into other organisms. � Large amounts of carbon dioxide are also dissolved in the world's oceans.

Primary Productivity • The rate at which plants and other photosynthetic organisms produce organic compounds (such as glucose) in an ecosystem. • Changes in regional and global climates and in atmospheric composition influence patterns of primary productivity Gross Productivity The entire photosynthetic production of organic compounds in an ecosystem Net Productivity The organic materials that remain after photosynthetic organisms in the ecosystem have used some of these compounds for their cellular energy needs (cellular respiration).

Food Chain and Web Dynamics � Organisms within food webs and food chains interact. � Food webs and food chains are dependent on primary productivity � Autotrophs (producers) manufacture their own food, while heterotrophs (consumers) must obtain organic molecules that have been synthesized by autotrophs.

� Once energy enters an ecosystem, it is passed from one organism to another in the form of chemical bonds, and much of the energy is converted to heat. � Overall, an average of 10% of organic matter is transferred from one trophic level to the next. � Organisms from different trophic levels (feeding levels) make up a food chain, and the length and complexity of food chains vary greatly. � Most often, trophic levels exist and are discussed in terms of food webs, or interactions of multiple food chains.

�Energy � Food in Food Chains chains are limited in the number of trophic levels that can be supported because so much energy is lost at each step that very little energy usually remains after three or four steps. � In theory, communities with higher productivity can support longer food chains �Ecological � Due Pyramids to the loss of useful energy at each trophic level, higher trophic levels generally have fewer individuals than lower levels.

Biomagnification Mercury, PCB, DDT

Ecosystem Stability � The diversity of species within an ecosystem may influence the stability of the ecosystem. ◦ Natural and artificial ecosystems with fewer component parts and with little diversity among the parts are often less resilient to changes in the environment

Chapter 56: The Biosphere Activity Pollution Acid Precipitation Destruction of the Tropical Forests The Ozone Hole Carbon Dioxide And Global Warming Introduced And Invasive Species Description and ONE Example Local Effects Global Effects

Human Impact on the Biosphere � Human activities impact ecosystems on local, regional and global levels � As human populations have increased in numbers, their impact on habitats for other species have been magnified. � In turn, this has often reduced the population size of the affected species and resulted in habitat destruction and, in some cases, the extinction of species. � Human impact accelerates change at local and global levels

The Pacific Garbage Patch

� Geological and meteorological events impact ecosystem distribution ◦ El Nino and La Nina �Cyclic warming (El Nino) or cooling (La Nina) of eastern pacific �Affects global climate patterns and can result in drought, severe winters, flooding, tropical storm tracks ◦ Continental drift �Continents have moved and continue to move into different areas �Climates changes and this affects populations ◦ Meteor impact on dinosaurs �Global temperature change resulted in extinction of dinosaurs �Permitted mammals and smaller reptiles to survive

Examples of Human Impact � � � Logging Slash and burn agriculture Urbanization Monocropping ◦ Agricultural practice of growing a single crop year after year on the same land, without rotation through other crops ◦ Depletes soil of nutrients ◦ Creates an ideal niche for parasites and pests ◦ Requires more fertilization and pesticide use Infrastructure development ◦ dams, transmission lines, roads � Introduced species ◦ Exploit a new niche free of predators or competitors, thus exploiting new resources. � Introduction of new diseases can devastate native species.

� Introduced ◦ ◦ ◦ (Invasive) Species Purple Loosestrife Phragmities Asian Shore Crab Asian Long Horn Beetle Kudzu (Southern U. S. )