Energy Flow and Populations

Autotrophs (Producers) Flow of Energy in an Ecosystem Energy in an Ecosystem Autotrophs (Producers) Organism that collects energy from sunlight or inorganic substances to produce food Heterotrophs (Consumers) Organism that gets it energy requirements by consuming other organisms A lynx is a heterotroph.

Also known as Detritivores Flow of Energy in an Ecosystem and return nutrients to the soil, air, and water where the nutrients can be reused by organisms. Decomposers eat fragments of dead matter in an ecosystem, Fungus Also known as Detritivores

Food chains and food webs model the energy flow through an ecosystem. Flow of Energy in an Ecosystem Models of Energy Flow Food chains and food webs model the energy flow through an ecosystem. Each step in a food chain or food web is called a trophic level. Producers Primary Consumers Secondary Consumers Tertiary Consumers Tertiary Consumers Secondary Consumers Primary Consumers Producers

The length of a Food chains varies with each ecosystem. Flow of Energy in an Ecosystem Food Chains A food chain is a simple linear model that shows how energy flows through an ecosystem. The length of a Food chains varies with each ecosystem.

Food Chains

Flow of Energy in an Ecosystem Food Webs A food web is a model representing the many interconnected food chains and pathways in which energy flows through a group of organisms.

Food Webs

90% of energy is lost as heat 10% is available energy Flow of Energy in an Ecosystem Ecological Pyramids A diagram that can show the relative amounts of energy, biomass, or numbers of organisms at each trophic level in an organism 90% of energy is lost as heat 10% is available energy

The number of organisms of a certain species per unit area Population Dynamics Population Density The number of organisms of a certain species per unit area

Population Dynamics Population Ranges A species might not be able to expand its population range because it cannot survive the abiotic conditions found in the expanded region. Common dolphin Pupfish

Population-Limiting Factors Population Dynamics Population-Limiting Factors There are two categories of limiting factors—density-independent factors and density-dependent factors.

Density-Independent Factors Population Dynamics Density-Independent Factors Any factor in the environment that does not depend on the number of members in a population per unit area is a density-independent factor. Weather events Fire Human alterations of the landscape Air, land, and water pollution

Density-Dependent Factors Population Dynamics Density-Dependent Factors Any factor in the environment that depends on the number of members in a population per unit area is a density-dependent factor. Biotic factors Disease Competition Parasites

Population Growth Rate Population Dynamics Population Growth Rate The population growth rate (PGR) explains how fast a given population grows.

Exponential Growth Model Population Dynamics Exponential Growth Model 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 Dynamics Logistic Growth Model The population’s growth slows or stops following exponential growth, at the population’s carrying capacity.

Population Dynamics A population stops increasing when the number of births is less than the number of deaths or when emigration exceeds immigration.

Population Dynamics Carrying Capacity The maximum number of individuals in a species that an environment can support for the long term is the carrying capacity. Carrying capacity is limited by the energy, water, oxygen, and nutrients available.

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