Chapter 3: The Biosphere

The Study of Ecology

What is Ecology?

• Ecology is the scientific study of interactions among organisms and between organisms and their environment

Why do we study ecology?

• We live in the natural world and use its resources (water, space,food, etc)

• The natural world effects our lives (weather, fire, economy)

• To protect biodiversity

Levels of Organization

• Ecologists recognize there is a hierarchy of organization in the environment: biosphere, biome ecosystem, community, population, and organisms

Levels of Organization

What is a Biosphere?

• Part of Earth in which life exists including land, water, and air or atmosphere

What is a Biome?

• A group of ecosystems that have the same climate and similar dominant communities

Temperate Forest Tundra

What is an Ecosystem?

• A collection of all organisms that live in a particular place, which includes the nonliving, or physical, environment

What is a Community and a Population?

• A community is assemblage of different populations that live together in a defined area

• A population is a group individuals that belong to the same species and live in the same area

How Do We Study Ecology?

• Observing• Experimenting• Modeling (Ecological

phenomena that occur over long periods of time)

How Do Organisms Obtain Energy in an Ecosystem?

• Sunlight is the main energy source for life on Earth

• Autotrophs will then use the energy from the sun (or chemicals) to make their own food

• Autotrophs are also known as producers• Examples of autotrophs: plants, algae,

cyanobacteria

How Do Organisms Obtain Energy in an Ecosystem?

• Autotrophs use photosynthesis to convert sunlight, carbon dioxide, and water into oxygen and carbohydrates

How Do Organisms Obtain Energy in an Ecosystem?

• What if there is no light in the ecosystem?

• The autotrophs will use chemosynthesis, which is a process that uses chemical energy to produce carbohydrates (ex: bacteria living in volcanic vents)

How Do Organisms Obtain Energy in an Ecosystem?

• Organisms that rely on other organisms for energy are known as consumers or heterotrophs

Types of Heterotrophs

• Herbivores- consume only plants• Carnivores- consume only meat• Omnivores- consume both plants and animals• Detritivores- consume plant and animal

remains (earthworms, mites, crabs)• Decomposer= breaks down organic matter to

obtain energy (bacteria & fungi)

Feeding Relationships

• Energy in an ecosystem flows in one direction (from sun to the heterotrophs)

• Food chain- a series of steps in which organisms transfer energy by eating and being eaten

Food Chain

Food Web

Transfer of Energy

• Each step in a food chain or food web is called a trophic level

• Autotrophs make up the first trophic level, consumers make up 2nd, 3rd, 4th or higher levels

• Only about 10% of energy is transferred to organisms at the next trophic level

Transfer of Energy

• If 10% of solar energy is captured by plants then animals who eat the grass gain only 10% of that energy (1%), animals who those animals gain 10% from that (.1%)

• 10% --> 1% --> .1%

What is Biomass?

• Biomass is the total amount of living tissue within a given trophic level

• A biomass pyramid can show you much food is available to each trophic level

Recycling Matter in the Biosphere

• Elements, chemical compounds, and other forms of matter are passed from one organism and from one part of the biosphere to another in biogeochemical cycles

Important Biogeochemical Cycles

• Water cycle

• Carbon Cycle

• Nitrogen Cycle

• Phosphorus Cycle

The Water Cycle

The Water Cycle

• Water moves between the ocean, atmosphere, and land

• Water evaporates from bodies of water into the atmosphere

• Water can also enter the atmosphere through transpiration (process by which water is lost through the leaves of plants)

Nutrient Cycles

• A nutrient is a chemical substance that an organism needs to sustain life

• Important nutrient cycles– Carbon Cycle– Nitrogen Cycle– Phosphorus Cycle

The Carbon Cycle

• Carbon’s Roles– Ingredient in living tissue

– Important component of animal skeletons (CaCO3)

– Important component of the atmosphere (CO2)

The Carbon Cycle

• Carbon enters the atmosphere by:– Respiration– Geochemical processes– Human activities

• Carbon is taken up by:– Photosynthesis– Burial and decomposition of dead organisms

(formation of fossil fuels)

The Carbon Cycle

CO2 inAtmosphere

CO2 in Ocean

The Nitrogen Cycle

• The roles of nitrogen:– Important component of amino acids

– Major component of fertilizer (NO3-)

– Major component of atmosphere (N2)

The Nitrogen Cycle

• Nitrogen gas (N2) cannot be used by plants so it must be converted into a usable form

• Soil bacteria convert nitrogen gas into ammonia (NH3) in the process of nitrogen fixation

• More soil bacteria convert ammonia into nitrates (NO3

-) and nitrites (NO2-) a usable form

• Other soil bacteria then convert nitrates and nitrites back into nitrogen gas, which is known as denitrification

The Nitrogen Cycle

The Phosphorus Cycle

• Roles of Phosphorus– Important component of DNA and RNA

• Does not enter atmosphere (gas)• Steps

– Phosphorus is found in rocks and sediment which gets moved by water

– Plants absorb phosphorus in the form of phosphate from soil and water

– Heterotrophs consume plants

What is a Limiting Nutrient?

• A nutrient that is scarce of cycles very slowly

• When an aquatic ecosystem receives a large amount of a limiting nutrient it immediately increases the amount of algae, which is known as algal bloom

Algal Bloom

• What is the result of algal bloom?