EcosystemsEcosystems

Science 10Science 10

BiosphereBiosphere

This is the title given to the area of the earth This is the title given to the area of the earth where life exists.where life exists.

It is about 20km thick, from the bottom of the It is about 20km thick, from the bottom of the oceans to the highest point in the atmosphere oceans to the highest point in the atmosphere where life can be found.where life can be found.

The biosphere can be divided into The biosphere can be divided into biomes.biomes.

BiomesBiomes These are divided according to the type of vegetation These are divided according to the type of vegetation

which can be found in its midst.which can be found in its midst.

There are three main types:There are three main types: TerrestrialTerrestrial FreshwaterFreshwater MarineMarine

Each of these biomes can be divided into a wide variety Each of these biomes can be divided into a wide variety of of ecosystems.ecosystems.

EcosystemsEcosystems

This includes all the organisms in an area that interact This includes all the organisms in an area that interact with each other and with their environment.with each other and with their environment.

The fuel for ecosystems is the The fuel for ecosystems is the sun.sun.

Sunlight is captured by green plants for photosynthesis Sunlight is captured by green plants for photosynthesis and stored as carbohydrate energy.and stored as carbohydrate energy.

This energy then gets passed on as herbivores eat plants This energy then gets passed on as herbivores eat plants and carnivores eat the herbivores.and carnivores eat the herbivores.

Two main factors in an Two main factors in an ecosystemecosystem

Abiotic factors- Abiotic factors- these are all of the these are all of the nonlivingnonliving aspects of the ecosystem that affects the aspects of the ecosystem that affects the organism.organism. These include water, carbon dioxide, minerals, These include water, carbon dioxide, minerals,

light, temperature, wind, space, etc…light, temperature, wind, space, etc…

Biotic factors- Biotic factors- these are all of the these are all of the living living organisms in an ecosystemorganisms in an ecosystem

Modes of NutritionModes of Nutrition

AutotrophsAutotrophs Capture sunlight or chemical energyCapture sunlight or chemical energy ProducersProducers

HeterotrophsHeterotrophs Extract energy from other organisms or organic Extract energy from other organisms or organic

wasteswastes ConsumersConsumers, decomposers, detritivores, decomposers, detritivores

Simple Simple Ecosystem Ecosystem

ModelModelenergy input from sun

nutrientcycling

PHOTOAUTOTROPHS(plants, other producers)

HETEROTROPHS(consumers, decomposers)

energy output (mainly heat)

Consumers Consumers

Herbivores Herbivores

Carnivores Carnivores

ParasitesParasites

Omnivores Omnivores

DecomposersDecomposers

Detritivores Detritivores

SPRING

rodents, rabbits

fruits

insects

birds

SUMMER

rodents, rabbits

fruits

insects

birds

Seasonal variation in the diet of an omnivore (red fox)

Does one ecosystem hold more energy than Does one ecosystem hold more energy than another?another?

How is energy stored and transferred within an How is energy stored and transferred within an ecosystem?ecosystem?

How does it leave an ecosystem?How does it leave an ecosystem?

These types of questions are important These types of questions are important because the energy that is captured by plants because the energy that is captured by plants through photosynthesis determines the amount through photosynthesis determines the amount of energy that is available for all other of energy that is available for all other organisms in the ecosystem.organisms in the ecosystem.

Human survival depends on the amount of Human survival depends on the amount of energy that is stored in agricultural ecosystemsenergy that is stored in agricultural ecosystems

Compared with animals, green plants produce more energy per unit Compared with animals, green plants produce more energy per unit land area. (see results from graph exercise)land area. (see results from graph exercise)

Thus, most of the energy in an agricultural ecosystem is found in Thus, most of the energy in an agricultural ecosystem is found in the crops, such as the field of corn.the crops, such as the field of corn.

Only a portion of this energy is transferred to livestock that eat the Only a portion of this energy is transferred to livestock that eat the plants.plants.

As a result, animals and animal products contain less energy than As a result, animals and animal products contain less energy than plant and plant products that are raised on the same amount of land.plant and plant products that are raised on the same amount of land.

This begs the question; Why is only some of This begs the question; Why is only some of the original energy transferred to the plant the original energy transferred to the plant eaters?eaters?

What happens to it?What happens to it?

Why is some lost from level to level?Why is some lost from level to level?

Trophic LevelsTrophic Levels

Ecosystems can be thought of as being made Ecosystems can be thought of as being made

up of several feeding levels, or up of several feeding levels, or Trophic levelsTrophic levels

All the organisms at a trophic level are the All the organisms at a trophic level are the

same number of steps away same number of steps away from the energy from the energy

input into the systeminput into the system

Trophic LevelsTrophic Levels

Producers (autotrophs) make up the first trophic level.Producers (autotrophs) make up the first trophic level.

Primary consumers (heterotrophs) feed at the second Primary consumers (heterotrophs) feed at the second

trophic level.trophic level.

Secondary consumers (heterotrophs) feed at the third Secondary consumers (heterotrophs) feed at the third

trophic level and so on.trophic level and so on.

All the organisms at a trophic level are the All the organisms at a trophic level are the same number same number

of steps away of steps away from the energy input into the systemfrom the energy input into the system

Most of the energy that enters each trophic level is used by the organisms at Most of the energy that enters each trophic level is used by the organisms at this level this level just to stay alivejust to stay alive..

The organisms need energy to The organisms need energy to movemove from place to place, from place to place, growgrow, , reproducereproduce, , and and carry out other activitiescarry out other activities..

Some of the energy Some of the energy cannot be used and passes out of the organisms as waste.cannot be used and passes out of the organisms as waste.

Only a small percentage of the energy remains stored in each organism as Only a small percentage of the energy remains stored in each organism as body tissues.body tissues.

It is this energy that is available as potential food for consumers in the next It is this energy that is available as potential food for consumers in the next trophic level.trophic level.

Food ChainFood Chain

A straight line sequence A straight line sequence

of who eats whom of who eats whom

Simple food chains are Simple food chains are

rare in naturerare in nature

MARSH HAWK

UPLAND SANDPIPER

GARTER SNAKE

CUTWORM

FoodFoodWebWeb

Many organisms eat a variety of foods and consume organisms from many different trophic levels.

The complex relationship is demonstrated via a food web.

Decomposer Food ChainsDecomposer Food Chains

Organisms that receive energy from dead plant and Organisms that receive energy from dead plant and animal materialanimal material

Make up majority of food chainsMake up majority of food chains Scavengers eat the remaining energy in large dead Scavengers eat the remaining energy in large dead

organismsorganisms Ex: Vultures eat the carcasses of dead animalsEx: Vultures eat the carcasses of dead animals

Decomposers – types of organisms that break down Decomposers – types of organisms that break down cells to extract remaining energycells to extract remaining energy Ex: fungi and bacteriaEx: fungi and bacteria

Two Types of Food WebsTwo Types of Food Webs

Producers (photosynthesizers)

Producers (photosynthesizers)

herbivores

carnivores

decomposers

decomposers

detritivores

ENERGY OUTPUT ENERGY OUTPUT

Grazing Food Web Detrital Food Web

Primary ProductivityPrimary Productivity

GrossGross primary productivity is primary productivity is

ecosystem’s total rate of photosynthesisecosystem’s total rate of photosynthesis

NetNet primary productivity is rate at which primary productivity is rate at which

producers store energy in tissues in producers store energy in tissues in

excess of their aerobic respirationexcess of their aerobic respiration

Primary Productivity VariesPrimary Productivity Varies

Seasonal variationSeasonal variation

Variation by habitatVariation by habitat

The harsher the environment, the The harsher the environment, the

slower plant growth, the lower the slower plant growth, the lower the

primary productivity primary productivity

Pyramids Pyramids

Pyramid of Numbers – shows how the greatest Pyramid of Numbers – shows how the greatest number of organisms is in the first trophic level, least number of organisms is in the first trophic level, least number on top of the trophic levelnumber on top of the trophic level

Pyramid of Biomass –shows the relative mass of the Pyramid of Biomass –shows the relative mass of the organisms at each trophic levelorganisms at each trophic level

Pyramid of Energy Flow – shows how the energy Pyramid of Energy Flow – shows how the energy available at each trophic level is greatest at the available at each trophic level is greatest at the bottom of the food chain and least at the topbottom of the food chain and least at the top

Pyramid of BiomassPyramid of Biomass Aquatic ecosystem in FloridaAquatic ecosystem in Florida Site of a long-term study of a grazing food webSite of a long-term study of a grazing food web

5

decomposers, detritivores(bacteria, crayfish)

1.5

1.1

37

third-level carnivores(gar, large-mouth bass)

second-level consumers(fishes, invertebrates)

first-level consumers(herbivorous fishes,turtles, invertebrates)

809 primary producers (algae,eelgrass, rooted plants)

Biomass pyramid

Pyramid of Energy FlowPyramid of Energy Flow

Primary producers trapped about 1.2 percent of Primary producers trapped about 1.2 percent of the solar energy that entered the ecosystemthe solar energy that entered the ecosystem

About 10% passed on to next levelAbout 10% passed on to next level

detritivores

21

383

3,368

20,810 kilocalories/square meter/year

top carnivores

carnivores

herbivores

producers

decomposers

All Heat in the EndAll Heat in the End

At each trophic level, the bulk of the energy At each trophic level, the bulk of the energy received from the previous level is used in received from the previous level is used in metabolismmetabolism

This energy is released as heat energy and lost This energy is released as heat energy and lost to the ecosystemto the ecosystem

Eventually, all energy is released as heatEventually, all energy is released as heat

Work on questions 1-4 page 274Work on questions 1-4 page 274

Work on questions 5-10 pages 275-276.Work on questions 5-10 pages 275-276.

Complete “Going with the Flow” worksheetComplete “Going with the Flow” worksheet

Feeding levelsFeeding levels

First trophic level – always plantsFirst trophic level – always plants Second trophic level – primary consumers Second trophic level – primary consumers Third trophic level – secondary consumersThird trophic level – secondary consumers

Energy flows through the food chain but only about Energy flows through the food chain but only about 10% of the energy is passed on from one trophic level 10% of the energy is passed on from one trophic level to the next.to the next. Ex: Plant has 100kJ, caterpillar uses 10% for life processes, Ex: Plant has 100kJ, caterpillar uses 10% for life processes,

90% is lost as heat or waste90% is lost as heat or waste

Carrying CapacityCarrying Capacity Can any population of organisms keep growing forever? Can any population of organisms keep growing forever?

What might limit its numbers?What might limit its numbers? The largest number of individuals in a species that an The largest number of individuals in a species that an

environment can support is called the carrying capacity.environment can support is called the carrying capacity. 4 factors that determine carrying capacity4 factors that determine carrying capacity

1.1. Materials/energy –limited by the amount of usable energy, water, Materials/energy –limited by the amount of usable energy, water, carboncarbon

2.2. Food Chains- population sizes at each trophic level (predators, Food Chains- population sizes at each trophic level (predators, herbivores)herbivores)

3.3. Competition – Intraspecific (same species)/Interspecific (between Competition – Intraspecific (same species)/Interspecific (between species)species)

4.4. Density – how many organisms occupy a given space at a given timeDensity – how many organisms occupy a given space at a given time

Factors which can limit the Factors which can limit the growth of a population growth of a population

include:include: predation shortage of food disease lack of water lack of space

Factors That Affect the Size of a Factors That Affect the Size of a PopulationPopulation

Density Dependent: (overcrowding,)Density Dependent: (overcrowding,) If population density increases it can cause a decrease in If population density increases it can cause a decrease in

the populationthe population Increased stress = spread of disease and parasitesIncreased stress = spread of disease and parasites Increased aggression = neglect of offspringIncreased aggression = neglect of offspring

These factors decrease the population numbersThese factors decrease the population numbers Density IndependentDensity Independent

Events that can decrease population numbers that are not Events that can decrease population numbers that are not dependent on the size of the population (ie. Forest fire)dependent on the size of the population (ie. Forest fire)

Please work on questions 1-4 page 290Please work on questions 1-4 page 290

Finish for homeworkFinish for homework