ENVIRONMENTAL

BIOLOGY

Part 4

Overview:

A) THE BIOSPHERE

B) POPULATION ECOLOGY

C) COMMUNITY ECOLOGY

D) ECOSYSTEM ECOLOGY

E) THE CARBON & NITROGEN CYCLES

F) ECOLOGICAL TECHNIQUES

G) SIMPSON’S RECIPROCAL INDEX

H) LOCAL ECOLOGY

I) BIOLOGICAL DIVERSITY

Two processes proceed concurrently in ecosystems:

The movement of:

1. ENERGY

linear

renewed all the time

2. NUTRIENT ELEMENTS

cyclic

originates from the abioticcomponent

SUNLight

energy

Bioticcomponent

Heat

energy

Abioticcomponent

nutrients

ENERGY FLOW

Plants get energy directly from the sun.

These organisms get energy indirectly from the

sun.

The SUN is considered the ultimate source of energy as it:

provides energy to almost all

organisms.

Bacteria are the base of the food chain at hydrothermal vents.

These bacteria use sulfur compounds, particularly hydrogen

sulfide, a chemical highly toxic to most known organisms, to

produce organic material through the process of chemosynthesis.

http://en.wikipedia.org/wiki/Hydrogen_sulfidehttp://en.wikipedia.org/wiki/Chemosynthesis

harness energy from the sun

e.g. plants, algae

Producers:

Consumers: organisms that eat something else

e.g. animals

Ulva lactuca

Decomposers: return energy to the environment

e.g. fungus, bacteria

The terms detritivore and decomposer are often used interchangeably

Detritivores- small animals like

earthworms, crabs that feed on detritus

Detritus: fragments of decaying material

springtail

What do decomposers and detritivoreshave in common?

BOTH receive energy from decayed matter

Fungus: DECOMPOSER

Spider crab: DETRITIVORE

How do they differ?

Detritivores:eat the organic

matter

Decomposers:1. secrete enzymes to

digest organic matter 2. then absorb the

ensuing molecules

The decomposers are a special subset of detritivores that:

break the organic compounds in inorganic form and then

The decomposers are a special subset of detritivores that:

break the organic compounds in inorganic form and then

absorb whatever they need for nutrition

Consumers

Four types

Herbivore: eats only plants

E.g. Cows, horses

Carnivore: eats only meat

E.g. Polar bear

Omnivore: eats plants and animals

E.g. Humans, bears

Scavenger: carnivore that feeds on bodies of dead organisms

e.g. Vultures

Vultures

Food Chains & Food Webs

A Food Chain is the:

energy flow from one trophic level to the other

One organism at each trophic level.

What does an arrow show?

The direction of the energy transfer, NOT “what ate what”

Rose Aphid Ladybug

A Trophic Level

describes the position of the organism in relation to how it gets nutrients & energy

The main trophic levels are:

Primary producers

Consumers

Decomposers

Primary producers:

Photosynthesisers: -are autotrophs:

get their energy directly from sunlight

Heterotrophs:

consume, directly or indirectly, the energy-rich molecules made

by the primary producers

Consumers & Decomposers are:

Trophic Levels [Feeding Levels]

heterotrophs

autotrophs

Organisms in one trophic level feed in the same way

1st Trophic Level

2nd Trophic Level

Terrestrial food chain Aquatic food chain

3rd Trophic Level

4th Trophic Level

Two Types of Food Chain:

Grazing food chains

Detritus food

chains

Leaf litter

Two Types of Food Chain:

1. grazing food chains

grass rabbit fox eagle

2. detritus food chains

leaf litter earthworm blackbird

dead animal blowfly maggots frog

(detritus detritivore carnivore)

blowfly maggot

What is a Food Web?

When more than one organism is present at each trophic level

When compared to food chains, Food Webs are:

Reticulate (resembles a network)

more stable more resistant to

disruption

If all deer die , do bears starve

to death?

NO!!

Note how: energy flows in ONE direction BUT ALL the matter ends up in the detritivores & decomposers

Energy Losses in Ecosystem

only about 1%

How much of the solar energy falling on a leaf is used for photosynthesis?

What happens to the rest of the solar energy falling on a

green leaf?

The light energy which is not absorbed by a leaf is:

Sunlight 100%Reflected 15%

Evaporation 75%

Transmitted 5%

Can a plant absorb ALL wavelengths of light?

White Light

Leaf Pigments

Absorb Most

Colors

NO. Certain wavelengths of light cannot be

absorbed (e.g. green)

Why do leaves look green?

Green wavelength is reflected

Question:

Give FOUR reasons why not all the light energy reaching a plant can be used for photosynthesis.

1) Light is reflected away by the cuticle;

2) Light may not be of the correct wavelength such as the green wavelength;

3) Light is not trapped by chloroplasts but passes right through the leaf - transmitted;

4) Light heats up water inside the leaf and makes it evaporate.

What is the photosynthetic efficiency?

Sunlight 1880 x 106 kJ m-2 yr -1 Reflected

Evaporation

Transmitted

Photosynthesis 24 x 106 kJ m-2 yr -1

1880 x 106

24 x 106 100%

?

24 x 106

1880 x 106 x 100 = 1.3%

Why does a food chain rarely have more than 7 trophic levels?

Substantial losses in energy at every trophic

level

Energy is lost at each trophic level.

What could cause the energy to be lost?

Heat

Movement

Waste e.g. feces, urine

Respiration

Uneaten parts

e.g. bones, fur,

shells, wood

Which portion will be available to the next trophic level?

Energy Losses in Ecosystem

Only about 10% of energy passes through each step of a food chain

90% of energy is lost at each step

If the pea plant contains 100 units of energy, how much energy would be present in the hawk?

100 10 1 0.1 0.01

Why are energy losses greater in homeotherms(birds & mammals) than in poikilotherms (fish,

reptiles)? -have to do something to maintain body temperature

Homeotherms use a great proportion of food eaten to keep a constantly warm body temperature.

Heat

Heat

Question:

This cow has eaten 100 kJ of stored energy in the form of grass, and lost 63 kJ in the form of faeces, urine and gas. The energy stored in its body tissues is 4 kJ. So how much has been used up in respiration?

The energy released by respiration:

Eaten: 100

Lost: 63

Kept: 4

100 – (63 + 4) = 33 kJ

Question:

Only 4 kJ of the original energy available to the cow is available to the next stage, which might be humans.

What is the efficiency of this energy transfer?

Efficiency = 4⁄100 × 100 = 4%

Explain the following observation:Average efficiency of transfer from:

plants to herbivores = 10%

from animal to animal = 20%

Herbivores are less efficient than carnivores as they eat grass having material which is not digestable(lignin & cellulose).

10% 20%

QuestionThe diagram shows the transfer of energy through a cow. The figures are in kJ × 106 year–1.

Key: A = energy absorbed from the gutC = energy consumed in foodF = energy lost in faecesP = energy used in production of new tissueR = energy lost by respirationU = energy lost in urine

a) (i) Complete the following equation for the energy used in the production of new tissue. Use only the letters C, F, R and U. (1)

P = C – (U + F + R)

ii) Calculate the value of P. (2)

P = C – (U + F + R)

= 91.34 (0.03 + 57.06 + 30.51)

= 91.34 – 87.6

= 3.74 kJ x 106 year -1

Production Ecology

refers to the rate of generation of biomass (the total mass of organisms in a given area or volume) in an ecosystem per unit area per unit time

unit is: joules/m2/year (energy) or

g/m2/year (dry organic matter)

Productivity / Production

Primary:productivity of

autotrophs (plants)

Two types of Productivity:

Food eaten

CO2

H2OO2

Glucose formed

Secondary:productivity of

heterotrophs (animals)

is the rate at which energy is stored by primary producers in the form of

organic substances which can be used as food materials

Primary Productivity

the energy potentially available to the next trophic level

GPP

NPP

Gross Primary Production (GPP):

the rate at which plants store chemical energy and is entirely available for growth

Net Primary Production (NPP):

NPP = GPP - R

Glucose produced during photosynthesis(Gross Primary Production)

Some glucose is used to supply energy to drive

cellular processes(Respiration)

Remaining glucose available to be laid down as new material - biomass(Net Primary Production)

NPP = GPP - R

Net Primary Productivity

NPP = GPP - Respirationplant≈50% of GPP is used for respiration

Biomass / Standing Crop

the amount of dry organic matter per unit area present at a given time

the amount of stored food energy per unit area present at a given time

OR

Unit of biomass: g/m2

Unit of biomass: J/m2

Productivity and Biomass DO NOT mean the same!!

Productivity is the RATE at which organic matter forms.

There is no element of time involved in the definition of biomass.

Productivity refers to the rate of generation of biomass in an ecosystem per unit area per unit time. Its unit is joules/m2/year.

Biomass refers to the amount of dry organic matter per unit area present at a given time. Its unit is g/m2. There is no element of time involved in biomass.

It is rapidly grazed

Give a reason why an ecosystem can be highly productive but has a low biomass.

It is rapidly grazed

Secondary Production: The conversion of assimilated energy into new tissue by animals

Waste(faeces)

Total energy taken in

(food eaten)

Energy assimilated = Food eaten – Faeces

How much energy is available to the next trophic level?

Gross primary production (GPP)

Net primary production

(NPP)

Respiration, maintenance

REMEMBER:

Components of energy transfer between trophic levels

Energy from lower trophic level

Energy not used Gross energy intake

Egested energy Digested energy

Urinary waste Assimilated energy

Resting energy Activity Growth Reproduction

Maintenance orrespiration

Production

Comparisons of Community Production

Community Climate Kcal/m2/yr

Desert Arid 400

Lake Temperate 2,400

Deciduous

Forest

Temperate 4,800

Tropical

Rainforest

Tropical 20,000

Cropland Temperate 8,800

Salt marsh Temperate 12,000

Freshwater

marsh

Temperate 17,000

What is the correlation in each case?

Positive correlation

Coral Reef: High productivity

Factors that influence Primary Productivity include: Temperature

Intensity of sunlight (which varies seasonally)

Generalisations about Community Productivity

The tropics have among the most productive systems, in part because incident solar radiation is greater toward the equator.

The most productive temperate systems are marshes. Nutrients are continually brought in and wastes are flushed out as water moves through them.

Deserts and oceans are among the least productive systems. Little water in deserts and few nutrients in open oceans are responsible. Thus, 80% of the Earth’s surface is covered by the least productive systems.

Energy Flow Through A Grazing Food Chain

Energy Flow Through A Grazing Food Chain

WORKED OUT PROBLEM: FLOW OF ENERGY (kJ/m2/yr) IN A GRASSLAND

1) Find the gross primary production of grasses and herbs.

36x105 + 20.4x106 = 24x106 kJ/m2/yr

2) Find the photosynthetic efficiency (i.e. efficiency of conversion of incident solar energy to gross primary production.

1880x106 100%

24x106 ?

24x106__ x 100 = 1.3%1880x106

3) What is the net production of seed-eating birds, spiders and grasshoppers respectively?

i) Birds:

60x103 – 59.2x103 = 800 kJ/m2/yr

3) What is the net production of seed-eating birds, spiders and grasshoppers respectively?

ii) Spiders: 700 – 500 = 200 kJ/m2/yr

3) What is the net production of seed-eating birds, spiders and grasshoppers respectively?

iii) Grasshoppers:

444x103 - 374.3x103 = 69700 kJ/m2/yr

Pyramids

What are ‘Ecological Pyramids’?

diagrammaticrepresentations of feeding relationships and energy transfer through the biotic component of ecosystems

Three types of Ecological Pyramids:

1. Numbers

2. Biomass

3. Energy

Producers

Primary consumers

Secondary consumers

Pyramid of Numbers: Nos. at each trophic level

4th Trophic Level

3rd Trophic Level

2nd Trophic Level

1st Trophic Level

Tertiary Consumer 1 eagle

Secondary Consumer 8 frogs

Primary Consumer 29 grasshoppers

Producers

1500 blades of grass

What happens to the population size on moving up the pyramid?

4th Trophic Level

3rd Trophic Level

2nd Trophic Level

1st Trophic Level

Tertiary Consumer 1 eagle

Secondary Consumer 8 frogs

Primary Consumer 29 grasshoppers

Producers

1500 blades of grass

Decreases

Pyramid of Numbers may be inverted:

Inverted pyramid with

a LARGEproducer

Inverted pyramid with

PARASITES

Typical pyramid with a carnivore

How would you collect data to draw a pyramid of fresh biomass for a field ecosystem?

A quadrat is placed at random.

All organisms enclosed are collected.

Organisms are separated into various trophic levels: producers, herbivores & carnivores.

Organisms at each trophic level are weighed.

Biomass in g m-2 is calculated.

Procedure is repeated to get an average.

A pyramid is drawn to scale.

1. Observe an animal while it feeds.

How would you know to which trophic level an organism belongs?

2. Inspect mouthparts.

3. Dissect ONE animal and observe gut contents.

How is a pyramid drawn to scale?

Organisms Fresh biomass / g

Green plants 2250

Herbivores 240

Carnivores 38

Green plants: 2250/38 = 59 boxes

Herbivores: 240/38 = 6 boxes

Carnivores: 38/38 = 1 box

Divide each number by the smallest value.

Pyramid of Biomass

Why is the pyramid inverted in autumn?

Low food production by producers & a lot of grazers

Draw a pyramid of numbers & of biomass for this food chain:

Pyramid of Numbers

Rosebush Aphid Ladybird

Pyramid of Biomass

Rosebush

Aphid

Ladybird

90% Loss in energy at EACH trophic level

Pyramid of Energy

kJ/m2/day

Why does biomass decrease up a food chain?

As energy is consumed by the organisms at each trophic level, less energy is available to

organisms further along the food chain which thus supports a smaller biomass

Four reasons why the pyramid of energy:

is the ideal way of representing relationships between individuals because:-

1. it takes into account the rate of production (flow of energy in a specific time)

Forest

Energy FlowkJ/m2/day

Biomassgrams/m2

2. Comparison based on biomass may be misleadingbecause weight for weight two species may not have the same energy content

3. inverted pyramids are not obtained

Pyramid of Energy:

Density(No./m2)

Biomass(g/m2)

Energy flow(kJ/m2/day)

Soilbacteria

1012 0.001 4.2

Marinesnails

200 10.0 4.2

Different ecosystems can be compared and the relativeimportance of populations within one ecosystem canbe compared

For example, the great importance of soil bacteria interms of energy flow is not obvious from their smallbiomass

Pyramid of Energy:

4. input of solar energy can be added as an extra rectangle at the base of the pyramid

Criticisms of ecological pyramids

1. It is difficult to allocate a trophic level to many carnivores and omnivores which eat a varied diet.

2. Another major problem is where to place dead and waste material.

Way to show decaying material in a pyramid of biomass or energy.

Overview:

A) THE BIOSPHERE

B) POPULATION ECOLOGY

C) COMMUNITY ECOLOGY

D) ECOSYSTEM ECOLOGY

E) THE CARBON & NITROGEN CYCLES

F) ECOLOGICAL TECHNIQUES

G) SIMPSON’S INDEX

H) LOCAL ECOLOGY

I) BIOLOGICAL DIVERSITY

A simple definition of biodiversity:

is the number and types of organisms in an environment

Three levels of diversity:

Biological Diversity:

refers to the diversity of life in all its forms, levels and combinations

it must be expressed at three levels:

1) Ecosystem diversity

2) Species diversity

3) Genetic diversity

END OF SECTION