SUSTAINING ECOSYSTEMS

SUSTAINING ECOSYSTEMS

Earth's Life Support System Earth's major components

Ecosystem System of interaction among all living (biotic) organisms of an area and their interactions with the (abiotic) environment. Abiotic: non living components (ex: water, air, sun) Biotic: living components (ex: plants, animals, bacteria) Trophic level - feeding level for an organism Two principal concepts: 1. Flow of Energy 2. Cycling of Matter 20 Nov. 2008 Ecosystems.ppt 3

The earth receives about one one-billionth of the sun s energy output. 28% reflected by atmosphere & sea surface 71% powers physical processes heating soil, air, & water wind, ocean currents, evaporation, etc. < 1% trapped by photosynthesis (available to life). Flow of Energy:

Ecosystem Components Abiotic chemicals Photosynthesis Producers (autotrophs) Consumers (heterotrophs) Aerobic respiration Decomposers Copyright 2011 by Nelson Education Limited. Fig. 4-16 Main structural components of an ecosystem

Energy flows in ecosystems

Major components of aquatic ecosystems.

Major components of terrestrial ecosystems.

Energy input to Ecosystem = light Energy (thanks to photosynthesis) CO 2 + H 2 O + light sugar + O 2 Energy (potential) stored in covalent bonds of sugar molecules. Movement (Flow) from organism to organism by feeding. Ecosystems.ppt 9

Food Chain Is a model that represents the flow of energy from one organism to another. linear The arrows represent the direction of the energy transfer grass rabbit fox

Food Chains

Progressive Energy Loss

Nature s Building Blocks Physical and chemical changes Law of conservation of matter matter may change form, but it can neither be created nor destroyed First law of thermodynamics energy may be changed or moved from place to place, but during physical or chemical change it can neither be created nor destroyed Second law of thermodynamics each change in energy, results in degradation to less useful forms

THERMODYNAMICS THERMODYNAMICS is the study of energy transformations. There are 2 LAWS you need to know: Energy CANNOT be created or destroyed, it can only be transformed (changed). During any energy transformation, some energy is changed into unusable energy (mostly heat) that can t be passed on. So...the amount of energy available in each link of a food chain is LESS than the amount of energy available in the link before.

The 10% Rule If 10% of the energy can be transferred from one trophic level to the one above it, each trophic level must have 10x the energy as the one above it. The number of trophic levels depends upon the number of primary producers in the first trophic level. Biomes with small numbers of primary producers have short food chains

Trophic Classification 3 categories: 1. PRODUCERS 2. CONSUMERS 3. DECOMPOSERS

TROPIC LEVELS

PRODUCERS Almost every food chain begins with a PRODUCER. Only plants are producers since they are the only organisms capable of producing food for themselves. (Thanks to PHOTOSYNTHESIS) Also called AUTOTROPHES. They are found in the first TROPHIC LEVEL of all food webs and pyramids.

CONSUMERS Organisms that cannot produce their own food must consume it. So, organisms who eat other organisms are called CONSUMERS. Also know as HETEROTROPHES. Heterotrophes are found on all but the first trophic level (which is exclusively where producers are found).

Types of Consumers HERBIVORES eat only plants Called PRIMARY CONSUMERS. OMNIVORES eat plants AND animals and may also be found on the 2 nd trophic level along with the herbivores but may also be found at higher trophic levels.

Types of Consumers (cont.) CARNIVORES who eat herbivores are found in the 3rd trophic level. Called SECONDARY CONSUMERS. Carnivores who eat other carnivores are found in higher trophic levels and are called TERTIARY CONSUMERS.

Types of Consumers (cont.) Scavengers are animal (ex: vulture or coyote) that eats carcasses abandoned by predators digs through trash cans for food, etc., true scavengers seldom kill their own prey (but many animals are not exclusively scavengers).

Types of Consumers (cont.) DETRITIVORES eat the waste produced by other organisms and include DECOMPOSERS (which break down detritus to get nutrients for themselves but in the process release nutrients back into the soil and water which plants and algae use).

Categories of Consumers primary consumers: (herbivores) feed directly on producers; secondary consumers: (carnivores) feed on primary consumers; tertiary consumers: feed only on carnivores; omnivores: consumers that feed on both plants & animals; scavengers: feed on dead organisms; detritivores: feed on detritus (partially decomposed organic matter, such as leaf litter & animal dung). decomposers (saprobes): consumers that complete the breakdown & recycling of organic materials from the remains & wastes of other organisms;

In reality, each individual organism in an ecosystem is involved in MANY food chains which all interlock with each other to form a feeding relationship called a FOOD WEB. FOOD WEB

FOOD WEB

Take a good look at this food web diagram and create as many different food chains as you can.

Ecological Pyramids Represent the flow of energy through an ecosystem. Typically each trophic level has a certain amount of BIOMASS (dry weight of organic matter) Ecological efficiency- amount of usable energy transferred as biomass. Usually 10% at each transfer. Food chains and webs only have 4-5 trophic levels, because too little energy left to support top consumers.

PYRAMID OF ENERGY FLOW This pyramid measures the total chemical energy that flows through each trophic level. The transfer of available energy at each trophic level explains why food chains rarely have more than four links. A pyramid of energy flow shows the decrease in energy that is available to each successive trophic level.

Energy Pyramid for 10% Rule

One More Example How much energy is available for the humans at the top of the food chain? What does this mean? So your tuna sandwich (72 g) requires how many grams of phytoplankton (the aquatic autotroph)?

PYRAMID OF NUMBERS Why do you think some animals are large and others are small? Shows the relative population sizes of organisms at each link in a food chain. Populations of top level predators are typically very small, and animals may be widely spaced within their habitats. Top predators are highly susceptible to extinction.

INVERTED PYRAMID OF NUMBERS How do we get INVERTED pyramids of numbers?

PYRAMID OF BIOMASS Another way to measure the energy in an ecosystem combines the number with the size of an organism. This measure is called biomass. A pyramid of biomass shows that biomass decreases from each trophic level to the one above.

Pyramid of Biomass Each tier represents the standing biomass (total dry weight of all organisms) in a trophic level. Generally narrow sharply because energy transfers between trophic levels are so inefficient.

PYRAMID OF BIOMASS

INVERTED PYRAMID OF BIOMASS Why does this ecosystem not collapse?

Trophic levels: Pyramid of Energy

Trophic levels: Pyramid of Numbers

Trophic levels: Pyramid of Biomass

Summary of Ecosystem Structure

The story of the sea otters show how changes in a population in one part of a food web affects populations in other parts of the web. A linked series of events extended all the way from the fish to the seals, to the killer whales, to the otters, to the kelp forest. The population size of each species is continually adjusted by the species interactions with both its food supply AND the consumers that use IT as food.

Cycling of Matter Producers take up matter Photosynthesis CO 2 from air + H 2 O from water/soil sugar + O 2 Movement of matter through ecosystem Return of matter to inorganic form Aerobic respiration sugar + O 2 CO 2 to air + H 2 O to water/air Reservoirs/stores of matter

Carbon cycle

Hydrologic cycle

Nitrogen cycle