UNIT 2 – ECOLOGY Chapters 3 – 6

3.1: What is Ecology? Biosphere Biosphere—all life on Earth & all parts of Earth where life exists – Deep ocean  above mountains Ecology Ecology—study of organisms & their interactions

Levels of organization 1.Species 1.Species—similar organisms that can breed & produce offspring 2.Population 2.Population—group of the same species living in the same area 3.Community 3.Community—different populations living in an area 4.Ecosystem 4.Ecosystem—all organisms with their physical environment 5.Biome 5.Biome—group of ecosystems 6.Biosphere

Biotic & abiotic factors compose the environment – Biotic – Biotic—living parts in an ecosystem – Abiotic – Abiotic—nonliving parts in an ecosystem

3.2: Energy, Producers & Consumers Primary Producers autotrophs Plants, algae & some bacteria are autotrophs—capture energy from the Sun & convert it so others can use it – Use photosynthesis primary producers Autotrophs are primary producers—first producers of energy

Consumers heterotrophs Animals, fungi & most bacteria are heterotrophs—consume others to obtain energy Consumers can be: – Herbivores – Carnivores – Omnivores – Scavengers – Decomposers

3.3: Energy Flow in Ecosystems Food Chains & Food Webs Food chain Food chain—series of steps in transfer of energy – Primary producer  herbivore  carnivore – Plankton, algae or plants begin food chains Food webs Food webs—network of food chains in an ecosystem

Trophic Levels & Pyramids trophic level Each step in a food chain is a trophic level Pyramid of energy – Only about 10% of energy passes from one trophic level to the next

Pyramid of numbers – Lower trophic levels have more organisms than higher trophic levels

3.4: Cycles of Matter The Water Cycle Precipitation  evaporation & transpiration  condensation

The Carbon Cycle Movement of carbon in form of CO 2 Atmosphere  plants  organisms Burning fossil fuels releases excess CO 2 into atmosphere; promotes climate change

The Nitrogen Cycle nitrogen- fixation Bacteria in plant roots use nitrogen- fixation – Converts nitrogen to forms plants & animals can use

4.2: Niches & Interactions The Niche Habitat Habitat—general place where an organism lives Niche Niche—what the organism does & how it interacts with its environment resources – How it uses its resources—water, sunlight, light, food, space

Competition Competition occurs when organisms try to use the same resources Dividing resources limits competition

Predation & Herbivory Predation Predation—one animal feeds on another animal Herbivory Herbivory—herbivore feeds on producers

Symbioses Symbiosis Symbiosis—relationship where 2 species live closely together Mutualism Mutualism—both species benefit Parasitism Parasitism—one species benefits & the other species is harmed Commensalism Commensalism—one species benefits & the other is not harmed or helped

5.1: How Populations Grow Describing Populations Population density Population density—number of individuals in an area – Distribution can be random, uniform, or clumped

Population Growth Birthrate > deathrate = population grows Birthrate < deathrate = population shrinks Immigration Immigration—individuals move into an area Emigration Emigration—individuals exit an area

Types of Growth Exponential growth Exponential growth—the larger a population gets, the faster it grows – Ex: bacteria Population growth slows if birthrate decreases or deathrate increases Carrying capacity Carrying capacity—the maximum number of individuals of a species that an environment can support

5.2: Limits to Growth Limiting Factors Limiting factor Limiting factor—controls the growth of a population

Density-Dependent Factors Density-dependent limiting factors Density-dependent limiting factors—affect dense populations more than sparse populations Types of density-dependent factors: – Competition – Predation (predator & prey may have population cycles together) – Herbivory – Parasitism & disease

Density-Independent Factors Density-independent limiting factors Density-independent limiting factors—affect all populations regardless of density or size Types of density-dependent factors: – Natural disasters (hurricanes, floods, drought, etc.) – Wildfires

Chapter 6 The Effect of Human Activity Humans clear large areas of land for farming Growing cities spread and take away habitat Humans rapidly deplete nonrenewable resources for life conveniences

The Use of Resources Poor farming practice leads to soil erosion Deforestation Deforestation reduces the world’s forests biological magnification Water pollution causes biological magnification—pollutants are stored in body tissues Air pollution causes smog and acid rain

Biodiversity Biodiversity— Biodiversity—the variety of life Threats to biodiversity: – Habitat loss – Hunting & demand for products – Invasive species – Climate change