biologi

DEPARTEMEN PENDIDIKAN NASIONALUNIVERSITAS NEGERI SURABAYA

JURUSAN BIOLOGI - FMIPA 2012

14th MEETING

• You should be able to:1. Define the terms habitat, niche, population,

community and ecosystem, and describe examples of each;

2. Explain the term producer, consumer and trophic level, and state examples of these in specific food chain and food webs;

3. describe how energy is transferred through food chain and food webs;

4. explain how energy losses occur along food chains, and understand what is meant by efficiency of transfer;

5. describe how nitrogen is cycled within an ecosystem.

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Food Chainsand

Food Webs

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What is a Food Chain?

• A food chain is the path by which energy passes from one living thing to another.

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What’s in a Food Chain?

•Producers•Consumers•Decomposers

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Producers

• Producers make their own food

• Green plants use energy from the sun to make food

• Producers are on the bottom of the food chain

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Consumers

• Consumers hunt, gather, and store food because they cannot make their own.

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Three Types of Consumers

•Herbivores•Carnivores•Omnivores

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Herbivores

• Animals who eat plants such as:–grasshoppers–rabbits–squirrels–deer–pandas

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Carnivores

• Animals who only eat other animals such as:–tigers–lions–hawks–wolves–cougars

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Omnivores

• Animals who eat both plants and animals such as:–humans–bears

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Decomposers

• Microorganisms that are able to break down large molecules into smaller parts

• Decomposers return the nutrients that are in a living thing to the soil

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Let’s Lookat a

Food Chain• A food chain is a

simplified way to look at the energy

that passes from producers to consumers.

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Types of Food Chains

• Aquatic- Water-related food chains with sea plants and animals

• Terrestrial- Land-related food chains with land plants and animals

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Predator & Prey

• Predator- An animal that captures and eats other animals

• Prey- The animal that is captured and eaten

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What is a Food Web?

• A more realistic way of looking at the relationship of plants and animals in an environment

• Several food chains linked together

• A predator from one food chain may be linked to the prey of another food chain

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Food Webs• How many food chains can

you make from this food web?

NUTRIENT CYCLES

NUTRIENT CYCLES: ECOSYSTEM TO

ECOSPHERE• Nutrient cycling occurs at

the local level through the action of the biota.

• Nutrient cycling occurs at the global level through geological processes, such as, atmospheric circulation, erosion and weathering.

NUTRIENT CYCLES

• The atoms of earth and life are the same; they just find themselves in different places at different times.

• Most of the calcium in your bones came from cows, who got it from corn, which took it from rocks that were once formed in the sea.

• The path atoms take from the living (biotic) to the non-living (abiotic) world and back again is called a biogeochemical cycle.

Nutrients: The Elements of Life

• Of the 50 to 70 atoms (elements) that are found in living things, only 15 or so account for the major portion of living biomass.

• Only around half of these 15 have been studied extensively as they travel through ecosystems or circulate on a global scale.

A GENERALIZED MODEL OF NUTRIENT CYCLING IN AN

ECOSYSTEM• The cycling of nutrients in

an ecosystem are interlinked by an a number of processes that move atoms from and through organisms and to and from the atmosphere, soil and/or rocks, and water.

• Nutrients can flow between these compartments along a variety of pathways.

Nutrient Compartments in a Terrestrial Ecosystem

• The organic compartment consists of the living organisms and their detritus.

• The available-nutrient compartment consists of nutrients held to surface of soil particles or in solution.

• The third compartment consists of nutrients held in soils or rocks that are unavailable to living organisms.

• The fourth compartment is the air which can be found in the atmosphere or in the ground.

Uptake of Inorganic Nutrients from the Soil

• With the exception of CO2 and O2 which enter though leaves, the main path of all other nutrients is from the soil through the roots of producers.

• Even consumers which find Ca, P, S and other elements in the water they drink, obtain the majority of these nutrients either directly or indirectly from producers.

The Atmosphere Is a Source of Inorganic Nutrients

• The atmosphere acts as a reservoir for carbon dioxide (CO2), oxygen (O2) and water (H2O).

• These inorganic compounds can be exchanged directly with the biota through the processes of photosynthesis and respiration.

• The most abundant gas in the atmosphere is nitrogen (N2);about 80% by volume. Its entry into and exit from the biota is through bacteria.

Some Processes By Which Nutrients Are Recycled

• Cycling within an ecosystem involves a number of processes.

• These are best considered by focusing attention on specific nutrients.

CARBON, HYDROGEN AND OXYGEN CYCLES IN

ECOSYSTEMS• C, H & O basic elements of life; making up

from about 98% of plant biomass.• CO2 and O2 enter biota from the atmosphere.

• Producers convert CO2 and H2O into carbohydrates (CH2O compounds) and release O2 from water.

• Producers, consumers and decomposers convert CH2O compounds, using O2, back into CO2 and H2O.

CARBON, HYDROGEN AND OXYGEN CYCLES IN ECOSYSTEMS

• Carbon and oxygen cycle come out of the air as carbon dioxide during photosynthesis and are returned during respiration.

• Oxygen is produced from water during photosynthesis and combines with the hydrogen to form water during respiration.

PHOSPHOROUS CYCLE IN ECOSYSTEMS

• Phosphorus, as phosphate (PO4-3),

is an essential element of life.• It does not cycle through

atmosphere, thus enters producers through the soil and is cycled locally through producers, consumers and decomposers.

• Generally, small local losses by leaching are balanced by gains from the weathering of rocks.

• Over very long time periods (geological time) phosphorus follows a sedimentary cycle.

NITROGEN CYCLE IN ECOSYSTEMS

• Nitrogen (N2) makes up 78% of the atmosphere.

• Most living things, however, can not use atmospheric nitrogen to make amino-acids and other nitrogen containing compounds.

• They are dependent on nitrogen fixing bacteria to convert N2 into NH3(NH4

+).

Biological Sources of Soil Nitrogen

• Only a few species of bacteria and cyanobacteria are capable of nitrogen fixation.

• Some are fee-living and others form mutualistic associations with plants.

• A few are lichens.

Atmospheric Sources of Soil Nitrogen

• Lightning was the major source of soil nitrogen until recent times when the burning of fossil fuels became a major source of atmospheric deposition.

• Nitrogen oxides come from a variety of combustion sources that use fossil fuels. In urban areas, at least half of these pollutants come cars and other vehicles.

Agricultural Supplements to Soil Nitrogen

• Various forms of commercial fertilizer are added to agricultural fields to supplement the nitrogen lost through plant harvest.

• Crop rotation with legumes such as soybeans or alfalfa is also practiced to supplement soil nitrogen.

Biological Nitrogen Fixation

• Nitrogen fixation is the largest source of soil nitrogen in natural ecosystems.

• Free-living soil bacteria and cyanobacteria (blue-green “algae”) are capable of converting N2 into ammonia (NH3) and ammonium (NH4

+).

• Symbiotic bacteria (Rhizobium) in the nodules of legumes and certain other plants can also fix nitrogen.

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Nitrification

• Several species of bacteria can convert ammonium (NH4

+) into nitrites (NO2

-).

• Other bacterial species convert nitrites (NO2

-) to nitrates (NO3

-).

Uptake of Nitrogen by Plants

• Plants can take in either ammonium (NH4

+) or nitrates (NO3-)

and make amino acids or nucleic acids.

• These molecules are the building blocks of proteins and DNA, RNA, ATP, NADP, respectively.

• These building blocks of life are passed on to other trophic levels through consumption and decomposition.

Ammonification

• Decomposers convert organic nitrogen (CHON) into ammonia (NH3) and ammonium (NH4

+).

• A large number of species of bacteria and fungi are capable of converting organic molecules into ammonia.

Denitrification

• A broad range of bacterial species can convert nitrites, nitrates and nitrous oxides into molecular nitrogen (N2).

• They do this under anaerobic conditions as a means of obtaining oxygen (O2).

• Thus, the recycling of N is complete.

GLOBAL NUTRIENT CYCLES

• The loss of nutrients from one ecosystem means a gain for another. (Remember the law of conservation of matter.)

• When ecosystems become linked in this manor, attention shifts to a global scale. One is now considering the ECOSPHERE or the whole of planet earth.

THANK YOU