Biology

Chapter3

3.1 – What is Ecology?

Interactions and Interdependence

• Ecology – the study of interactions among organisms and their environment

• Oikos (ec) – Greek word meaning house

• Ology – means study of

Levels of Organization

• The levels of organization that ecologists study include:

• Individuals

• Species – group of similar organisms that can breed and produce fertile offspring

• Populations – group of individuals of the same species that live in the same area and interbreed

• Communities – different populations that live together in a defined area

• Ecosystem – The interaction of all the organisms and the environment in a given area

• Biome – a group of ecosystems that have the same climate

• Biosphere – part of Earth in which life exists including land, water and atmosphere

• It extends about 8km above the Earth’s surface to about 11km below

• If you could shrink earth to the size of an apple, the biosphere would be thinner than the apple’s peel

Biotic and Abiotic Factors

• Biotic Factors – all the living organisms in an ecosystem

• Example: tree, bird, bacteria, fungi

• Abiotic Factors – nonliving factors in an ecosystems

• Example: temperature, precipitation, wind, soil, sunlight, humidity

• Habitat – area where an organism lives

• Includes both biotic and abiotic factors

• Niche – the role and position a species has in its environment

• No two species can share the same niche in the same habitat

3.2 – Energy Flow

• Sunlight is the main energy source for life

• Autotrophs

• Make their own energy

• Convert sun energy into chemical energy

• Also called a producer

• Plants are the main autotrophs on land

• Algae are the main autotrophs in water

• Some autotrophs can produce food in the absence of light

• Chemoautotrophs – organisms use chemical energy to produce carbohydrates

• Performed by several types of bacteria

• Live in…

• Volcanic vents

• Deep ocean

• Hot springs

• Marshes

• Heterotrophs

• Get energy from other organisms

• Unable to make its own energy

• Also called consumers

• Types of Heterotrophs

• Herbivores

• Eats only plants

• Example: cows, deer, rabbits, bees, elephants, squirrels

• Carnivores

• Eats only animals

• Example: snakes, dogs, lions, crocodiles

• Omnivores

• Eats plants and animals

• Example: humans, bears, crows

• Detrivores

• Eat decomposing bits of organic matter

• Example: mites, earthworms, snails, crabs

• Decomposers

• Break down organic matter

• Example: bacteria and fungi

• Scavenger

• Ingest nonliving plants and animals

• Example: vulture, termite, beetle

Feeding Relationships

• Food Chain – a straight line series of steps by which energy is stored and passed on to higher trophic levels

• Food Web – a network of crossing interlinked food chains that shows all the possible feeding relationships at each trophic level

• Energy is passed through no more than four or five trophic levels

• Trophic Levels – step in a food chain or food wed

• Plants and other producers are 1st trophic level

• Consumers make up the 2nd, 3rd, or higher trophic levels

• Each consumer depends on the trophic level below it for energy

• Energy is transferred from one trophic level to another and is never 100%

• At each trophic level only 10% of the energy taken in by the organism is stored. The rest is used up during metabolism to process the energy

Ecological Pyramids

• Ecological Pyramid – a diagram that shows the relative amounts of energy or matter contained within each trophic level in a food chain or food web

• Example: Ecological Pyramids

Community Interactions

• Competition – occurs when organisms of the same or different species attempt to use the same resources

• Predator – eat other animals

• Prey – the animal a predator eats

• Symbiosis – relationship in which two species live closely together

• Three Types of Symbiosis

• Mutualism

• Both species benefit from the relationship

• Example: plants and bacteria on roots

Shark and fish

• Commensalism

• One organism benefits and the other is neither helped nor harmed

• Example: tree and bird nest

• Parasitism

• One organism lives on or inside another organism and harms it

• Example: tick, ringworm

Fig. 48.12, p. 862

3-3 Cycles of Matter

• Biogeochemical Cycles – process in which elements, chemical, and other forms of matter are passed from one organism to another and from one part of the biosphere to another

The Water Cycle

• Evaporation – process by which water changes from a liquid to a gas

• Transpiration – loss of water from plants by the process of evaporation

• Condensation – water vapor changes to a liquid

• Precipitation – water returns to the earth (rain, snow, hail)

The Carbon Cycle

• Carbon is released into the atmosphere by…

• Respiration

• Burning fossil fuels

• Volcanic activity

• Burning trees

• Carbon is taken out of the atmosphere by…

• Photosynthesis performed by plants

• Carbon is released into the ground by…

• Decomposition

• Carbon is taken out of the ground by…

• Mining oil and coal

• Roots of plants

OilCoal Root Uptake

Decomposition

Photosynthesis

RespirationBurning Trees

Burning Fossil Fuels

Volcanic Activity

CO2

Organism eats plants

C6H12O6

Nitrogen Cycle

• Gaseous nitrogen (N2)makes up 80% of the atmosphere

• Nitrogen Fixation

• Bacteria convert N2 to ammonia (NH3)

• This dissolves forming ammonium (NH4)

• Ammonification

• Bacteria degrade nitrogenous wastes and remains of organisms.

• Convert NH3 to NH4

• Nitrification

• Bacteria convert NH4 to nitrite (NO2) to nitrate (NO3)

• Denitrification

• Bacteria convert extra nitrates or nitrites (NO3, NO2) to N2

• N2 is released back into the atmosphere

Gaseous Nitrogen

N2

Ammonification

Bacteria convert wastes and decomposing organics to

NH3 → NH4

Nitrogen Fixation

Bacteria in the soil convert

N2 → NH3 → NH4

Denitrification

Bacteria convert

NO3 → N2

Nitrification

Bacteria convert

NH4 → NO2 → NO3

Autotrophs can take up NH4 and NO3

• Humans are harming the nitrogen cycle by:

• Deforestation

• Conversion of grasslands for agriculture

• Sewage enters waterways

• Fossil fuel burning

• Vehicles having combustion engines releases NO2

4-2 What Shapes an Ecosystem?

• Ecological Succession

• Succession – changes that occurs in a community over time

• Pioneer Species – first species to populate the area

• Climax Community – a stable mature community that undergoes little or no change in species

• Two Types of Succession

• 1. Primary Succession

• Succession that occurs on surfaces where no soil exists

• Example: rock surfaces formed after volcanoes erupt

• Secondary Succession

• Succession following a disturbance that destroys a community without destroying the soil

• Because soil already exists, secondary succession usually takes less time than primary succession

• Example: fires, floods, farming, construction, hurricanes, tornadoes