CHAPTER 18 Ecology. 18.1What is Ecology? 18.2The Abiotic Environment 18.3The Biotic Environment 18.4Energy and Nutrient Flow 18.5Ecological Pyramids 18.6Nutrient

CHAPTER 18Ecology

18.1 What is Ecology?

18.2 The Abiotic Environment

18.3 The Biotic Environment

18.4 Energy and Nutrient Flow

18.5 Ecological Pyramids

18.6 Nutrient Cycling in an Ecosystem

18.7 Carbon Sinks

Chapter 18

Ecology

Learning Outcomes

After this section, you should be able to:

• define the terms ecology, habitat, population, community and ecosystem; and

• understand the link between habitat, population, community and ecosystem.



Ecology: The study of the interactions of organisms with one another, as well as with their environment

Ecology

• All organisms in this world are interdependent on one another.

• What is interdependent?– Eg: Sharks and pilot fish


Environment

Abiotic environmentconsists of physical factors such as light intensity, water availability and soil pH

Biotic environmentconsists of all the living things that an organism interacts with


Habitat: The place where an organism lives

Freshwater stream

Forests

Mangrove

Grassland

For example:

Habitat


Population

Community

Ecosystem

Population:A group of organisms of the same species living in a particular habitat

Community:All the populations of organisms living and interacting with one another in a particular habitat

Ecosystem:A community and its abiotic environment

Population, Community, Ecosystem

Chapter 18

Ecology







18.7 Carbon Sinks

• What environment do you like to live in?

Learning Outcome


• describe how the various components of the abiotic environment affect organisms.



Abiotic environment

Light intensity

Availability of water

Salinity of soil and/or water

Temperature

Oxygen content pH of soil and/or water


How does light intensity affect organisms?

Light intensity affects distribution and growth of plants and animals.

• Green plants exist only where there is adequate amount of sunlight.

• The growth of certain plants affects the distribution of animals in a location.

Light Intensity


Factors affecting water availability:

How does water availability affect organisms?

• Amount and pattern of rainfall • Air humidity

Organisms cannot live without water.

• Plants and animals that are found in environments where water is scarce (e.g. deserts) are adapted for survival in those environments.

Water

How does temperature affect organisms?


Temperature affects the rate of reaction of enzymes that control the physiological and metabolic activities of organisms.

• Snakes hibernate in winter.

• Deciduous trees lose their leaves before winter.

Temperature


Oxygen is needed for respiration to occur.

mud surface

pore for gaseous exchange

How does oxygen content affect organisms?

• Mangrove plants have their roots buried in oxygen-poor mud.

• Mangrove plants have roots with pneumatophores to ensure that the roots get enough oxygen.

• Pneumatophores are breathing roots that project above the mud surface.

Oxygen


Salinity refers to the salt concentration of water. It affects the movement of salt and water in and out of the cells of organisms living in water.

Freshwater bony fish faces problems of:

Uptake of salts by cells in the gills

How does salinity affect organisms?

• Salt loss from cells

• Excess water entering cells

Kidney reabsorbs salts and produces large amount of dilute urine

Salinity


Marine bony fish faces problems of:

Seawater is absorbed in the intestines

How does salinity affect organisms?

• Water loss from cells

• Excess salt entering cellsKidney excretes salts and produces a small amount of concentrated urine

Salinity


How does pH affect organisms?

• Plants like blueberry and orchid grow better in acidic soil.

• Several microorganisms have been found to thrive in highly acidic conditions. Such microorganisms are called acidophiles.

pH refers to the acidity or alkalinity of a solution. Most organisms can only survive within a range of optimum pH.

pH

Chapter 18

Ecology







18.7 Carbon Sinks

Learning Outcome


• describe how the biotic environment affects organisms.


• Which interactions do you like?


The living or biotic environment comprises of all the living organisms that an organism interacts with.

Organisms interact with one another in various ways.

Watch the following videos and determine if the interactions are beneficial or harmful.

Interaction between the birds and various organisms

Interaction between the carnivorous plants and insects

URL URL

Biotic Environment

http://www.youtube.com/watch?v=Qqa0OPbdvjw&feature=player_embedded

http://www.youtube.com/watch?v=ktIGVtKdgwo&feature=related


The populations in a community live interdependently.

A change in one population would affect the other populations in the community.

The equilibrium in a community is like a web, breaking a single strand will affect the whole system.

Biotic Environment

Chapter 18

Ecology







18.7 Carbon Sinks

Learning Outcomes


• explain the terms producer, consumer, and trophic level in the context of food chains and food webs;

• describe the non-cyclical nature of energy flow.


18.4

Energy and nutrients are transferred in the following direction via feeding.

Living organisms in an ecosystem can be categorised into the following groups:

Producers

Consumers

Decomposers

Energy and Nutrient Flow

18.4

• Convert light energy from the Sun into chemical energy in food

• All food chains start with producers.

• Examples include green plants and green algae.

Producers


18.4

• Obtain energy by feeding on other organisms

• Three types:• Primary consumers (herbivores): Animals that feed

on plants.

• Secondary consumers (carnivores): Animals that feed on primary consumers.

• Tertiary consumers (carnivores): Animals that feed on other carnivores.

Consumers


18.4

Decomposers

• Obtain energy by breaking down dead organisms, faeces and excretory products

• The decomposition process releases inorganic nutrients, such as carbon and nitrogen, for nutrient cycling.

• Examples of decomposers include fungi, bacteria and earthworms.


18.4 The Ecosystem

Food chain: A series of organisms through which energy is transferred in the form of food

It illustrates the feeding relationships among organisms. A food chain always begins with a producer.

grass toad snake

producerprimary

consumersecondary consumer

tertiary consumer

grasshopper

Food Chain

18.4

Trophic level: Each level or organism in a food chain

Generally, food chains do not have more than four trophic levels.

grass toad snake

producerprimary

consumersecondary consumer

tertiary consumer

grasshopper


Trophic Level

18.4

Food web: Interlinked food chains

URL


Food Web

green plant

caterpillar

grasshopper

aphid

spider

ladybird

bird

http://www.youtube.com/watch?v=8hCyY9r1xJY

Non-cyclic Energy Flow in an Ecosystem

• The Sun is the main energy source in an ecosystem.

• Light energy is converted into chemical energy by producers via photosynthesis.

• Energy from producers are passed from one trophic level to another via feeding.


• The flow of energy in an ecosystem is non-cyclic.

• Energy is lost to the environment as heat as it flows through the ecosystem.

Non-cyclic Energy Flow in an Ecosystem


Chapter 18

Ecology







18.7 Carbon Sinks

Learning Outcome


• describe and interpret pyramids of numbers, biomass and energy.


18.5

Pyramid of numbers

Ecological pyramids can be used to compare the trophic levels of a food chain.

Pyramid of energy

Pyramid of biomass

Ecological pyramids

Ecological Pyramids

18.5

grass plants (2 700 000)

hawks (10)

snakes (300)

rabbits (4 500)

trophic level 3

trophic level 4

trophic level 2

trophic level 1

• Allows the comparison of the number of organisms present in each trophic level at a particular time

• Constructed based on the number of organisms at each trophic level

Pyramid of Numbers

Ecological Pyramids

18.5

grass (5000 kg)

hawks (5 kg)

snakes (50 kg)

rabbits (500 kg)

• Allows the comparison of the mass of organisms present in each trophic level at a particular time

• Constructed based on the dry mass of organisms in each at a particular time

Pyramid of Biomass

Ecological Pyramids

18.5

Most ecological pyramids are pyramid-shaped, but there are exceptions.

A pyramid of numbers can be inverted if:

• organisms in one trophic level are parasitic on organisms of another trophic level, and

• many small organisms feed on a large organism.

A pyramid of biomass can be oddly shaped if:

• organisms in one trophic level have a high reproductive rate.

Ecological Pyramids

18.5

• Represents the total energy in each trophic level of a food chain over a certain period of time

grass plants (10 000 kJ)

hawks (10 kJ)

snakes (100 kJ)

rabbits (1 000 kJ)

secondary consumer

tertiary consumer

primary consumer

producers

Pyramid of Energy

Ecological Pyramids

18.5

Energy is lost to the environment as food is transferred from one trophic level to another.

Energy is lost to the environment:

• as heat during respiration,

• in uneaten body parts,

• through undigested matter egested by consumers, and

• through waste products excreted by consumers.

Ecological Pyramids

Pyramid of Energy

18.5

The pyramid of energy is always broad at the base and narrow at the top because energy is lost as we go down the food chain.

Grass (10 000kJ)

Hawks (10 k J)

Snakes (100 kJ)

Rabbits (1 000 kJ)

Energy lost

Ecological Pyramids

Pyramid of Energy

Chapter 18

Ecology







18.7 Carbon Sinks

Learning Outcome


• describe how carbon is cycled within an ecosystem.


18.6

The carbon cycle

Carbon is constantly removed from and released into the atmosphere in the form of carbon dioxide.

Hence, the concentration of carbon dioxide in the environment is not lost but continually recycled.

The carbon cycle is important because:

•It ensures a continuous supply of carbon dioxide for photosynthesis

•It enables energy to flow through the ecosystem.

Nutrient Cycling in an Ecosystem

18.6

Watch the following video on the carbon cycle.

List the various biological processes involved in the cycling of carbon as explained by Cole.

Mini activity


URL

http://www.youtube.com/watch?v=Xz0fn81BlIQ&feature=player_embedded

18.6

Carbon dioxide is removed from the environment via:

Photosynthesis

Fossil fuel

Green plants absorb carbon dioxide from the atmosphere and use it to produce carbon compounds.

Carbon compounds may be preserved as fossil fuels (e.g. coal, natural gas and oil)


FeedingWhen animals feed on green plants, the carbon compounds become part of their bodies.

The carbon cycle

18.6

photosynthesis feeding

death


The Carbon Cycle

18.6

Carbon dioxide is released into the environment via:

RespirationCarbon compounds such as glucose are broken down into carbon dioxide.

Combustion DecompositionThe combustion of fossil fuels such as coal and natural gas release carbon dioxide.

When organisms die, the dead matter is broken down into simple substances like carbon dioxide by decomposers.


The Carbon Cycle

18.6

respiration

combustion

death


respiration

decomposition

death

The Carbon Cycle

18.6

respiration

photosynthesis feeding

respiration

combustion

decomposition

death

death


The Carbon Cycle

Chapter 18

Ecology







18.7 Carbon Sinks

Learning Outcome


• define what carbon sinks are, and outline the role of oceans and forests as carbon sinks.

18.7 Carbon Sinks

What is a carbon sink?

•A carbon sink is an area that stores carbon compounds for an indefinite period.•It stores more carbon than it releases.

Carbon Sinks18.7

Oceans as carbon sinks

•Oceans are the largest carbon sinks on Earth.•The carbon dioxide that dissolves in the ocean’s water is absorbed and used by phytoplankton and algae in photosynthesis.•A portion of the carbon compounds found in oceans is buried in the seabed and is in the form of fossil fuels such as natural gas and oil.

Carbon Sinks18.7

Forests as carbon sinks

•Forests are also important carbon sinks.•Atmospheric carbon dioxide is absorbed by the plants and used in photosynthesis.•A large amount of carbon compounds is stored in trees. •Remains of dead trees form coal – a fossil fuel.

Carbon Sinks18.7

Chapter 18

Ecology

Documents

CHAPTER 18 Ecology. 18.1What is Ecology? 18.2The Abiotic Environment 18.3The Biotic Environment 18.4Energy and Nutrient Flow 18.5Ecological Pyramids 18.6Nutrient