CHAPTER 18 Ecology.

CHAPTER 18 Ecology

Chapter 18 Ecology 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

18.1 What is 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.

18.1 What is Ecology? Ecology
Ecology: The study of the interactions of organisms with one another, as well as with their environment Use the picture in the slide to revise on the terms population, community and ecosystem before revealing on the definition of ecology. Note: The next slide defines what makes up an environment.

All organisms in this world are interdependent on one another.
What is interdependent? Eg: Sharks and pilot fish What about Humans? Pilot fishes swim with sharks and feed off the scraps of meat left stuck within shark’s teeth. They help to clean and prevent diseases. The sharks provides security and ease movement in the sea for the pilot fish.

18.1 What is Ecology? Environment Abiotic environment
consists of physical factors such as light intensity, water availability and soil pH consists of all the living things that an organism interacts with Note: The environment is made up of the abiotic environment and the biotic environment. These two environments interact and influence each other. For example: light intensity affects the rate of photosynthesis in green plants, and the growth of organisms in a pond affects the concentration of dissolved oxygen in the pond. More examples will be given in the following sections.

18.1 What is Ecology? Habitat
Habitat: The place where an organism lives For example: Freshwater stream Forests Grassland Ask students to name animals that live in the places shown. Note: Organisms that live in: Freshwater streams: freshwater fish (such as catfish, tilapia, and codfish), shrimps, water snakes, water lilies, etc. Forests: Orangutans, deers, lizards, birds, fungi, fruit trees, orchids, etc. Grasslands: Zebras, gazelles, lions, coyotes, snakes, mice, hyenas, grasshoppers, herbaceous (non-woody) plants, grasses, etc. Mangroves: Mangrove trees, mangrove crabs, mud lobsters, oysters, algae, etc. Mangrove

Population, Community, Ecosystem
18.1 What is Ecology? Population, Community, Ecosystem Population: A group of organisms of the same species living in a particular habitat Population Community: All the populations of organisms living and interacting with one another in a particular habitat Community Note: Students can be prompted to deduce the link between the three terms before the boxes on the right are revealed. Ecosystem Ecosystem: A community and its abiotic environment

What environment do you like to live in?

The Abiotic Environment
18.2 The Abiotic Environment Learning Outcome After this section, you should be able to: describe how the various components of the abiotic environment affect organisms.

18.2 The Abiotic Environment Availability of water Light intensity Temperature Abiotic environment Oxygen content Salinity of soil and/or water pH of soil and/or water

18.2 The Abiotic Environment Light Intensity 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. Note: The growth of certain plants affects the distribution of animals in a location. For example, giant pandas live on a diet of bamboo shoots. Bamboo shoots require certain environmental conditions (including a range of acceptable light intensity) to grow. If the light intensity reaching the bamboo plants in a forest is lower than what is needed, the plants gradually decrease (or even, die off) and this will affect the giant panda population in that forest.

18.2 The Abiotic Environment Water How does water availability affect organisms? Factors affecting water availability: Amount and pattern of rainfall Air humidity Organisms cannot live without water. Note: How animals and plants that live in deserts are adapted for living in a desert: A camel can drink up to 100 liters of water at any one time. This allows them to survive for long periods without drinking water. Cacti have specialised leaves (i.e. needles) to reduce rate of transpiration and fleshy stems to help them store water. Plants and animals that are found in environments where water is scarce (e.g. deserts) are adapted for survival in those environments.

18.2 The Abiotic Environment Temperature 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. Note: Deciduous trees are trees that lose their leaves before winter (i.e. in autumn). Such trees are usually found in temperate countries (countries with four seasons). These trees lose their leaves in preparation for the decreased enzyme activity during the cold temperature in winter. Trees in Singapore do not lose their leaves because Singapore has warm weather throughout the year.

18.2 The Abiotic Environment Oxygen How does oxygen content affect organisms? Oxygen is needed for respiration to occur. 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. pore for gaseous exchange mud surface Note: Some fish (e.g. carp) that live in oxygen-poor waters get oxygen from the air by coming up to the surface to gulp air.

18.2 The Abiotic Environment Salinity How does salinity affect organisms? 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: Salt loss from cells Excess water entering cells Kidney reabsorbs salts and produces large amount of dilute urine Note: This concept can be linked back to the chapter on the movement of substances (Chapter 3, Biology Matters). Salt is lost from the fish cells via diffusion, water enters the fish cells via osmosis and salt from the water is taken into the fish cells via active transport. Uptake of salts by cells in the gills

18.2 The Abiotic Environment Salinity How does salinity affect organisms? Marine bony fish faces problems of: Water loss from cells Excess salt entering cells Kidney excretes salts and produces a small amount of concentrated urine Note: Marine fish = saltwater fish This concept can be linked back to the chapter on the movement of substances (Chapter 3, Biology Matters). Water is lost from the fish cells via osmosis, salt enters the fish cells via diffusion. The concept of homeostasis can also be discussed if time permits. Homeostasis: The maintenance of a constant internal environment. Seawater is absorbed in the intestines

18.2 The Abiotic Environment pH How does pH affect organisms? pH refers to the acidity or alkalinity of a solution. Most organisms can only survive within a range of optimum pH. 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. Note: ‘Phile’ comes from the Greek word ‘philos’ which means love. Helicobacter pylori is a bacteria that can survive in the human stomach. The human stomach has an acidity of about pH 2-4. However, helicobacter is not considered to be an acidophile as it does not ‘like’ the acidic condition. Instead, the bacteria have mechanisms that allow them to avoid the extreme acidic conditions of the stomach lumen. The bacteria stay close and adhere to the epithelial layer of the stomach where there is a thick mucous layer. The mucous layer has a pH that is closer to the neutral pH.

The Biotic Environment
18.3 The Biotic Environment Learning Outcome After this section, you should be able to: describe how the biotic environment affects organisms.

Which interactions do you like?

18.3 The Biotic Environment Biotic Environment 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 After watching the videos, ask some students to share their opinions on whether the interactions are beneficial or harmful. Note: Click on the first Video-URL button to be directed to a website where a video (length = 4:20 minutes) on the relationship between birds and various organisms, can be found. Namely, capybaras (0:00-1:48), hippopotamuses (1:49-2:41), zebras (2:42-3:00), and giraffes (3:01-4:20). Click on the second Video-URL button to be directed to a website where a video (length = 3:29 minutes) on two carnivorous plants – the Venus Flytrap and pitcher plants, can be found. Close and long-term interactions between two types of organisms are termed symbiosis. The symbiotic relationship can be: mutualistic – both organisms benefit from the interaction (e.g. oxpecker birds and hippos), Commensal – one organism benefits, the other is unaffected (e.g. birds and capybara), or parasitic – one organism benefits, the other suffers some negative effects (e.g. fleas and hippos). Note that the relationship between the carnivorous plants and insects are not parasitic as they are not long-term interactions. URL URL

18.3 The Biotic Environment Biotic Environment 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. Note: Example of how a change in one population will affect the other populations in the community (using the diagram on the slide): The pond community in the diagram is made up of three different populations; aquatic plants, snails and tadpoles. In the event that the snail population dies off due to disease, the aquatic plant population and tadpole population will increase. This is because snails feed on aquatic plants and snails compete with tadpoles for the aquatic plants.

Energy and Nutrient Flow
18.4 Energy and Nutrient Flow Learning Outcomes After this section, you should be able to: 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 Nutrient Flow Energy and nutrients are transferred in the following direction via feeding. Producers Living organisms in an ecosystem can be categorised into the following groups: Consumers Decomposers

18.4 Energy and Nutrient Flow Producers Convert light energy from the Sun into chemical energy in food All food chains start with producers. Examples include green plants and green algae. Note: Food chains are a representation of feeding relationships between organisms. Food webs are interlinked food chains. Both food chains and food webs are further discussed in slides 29-31

18.4 Energy and Nutrient Flow Consumers 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.

18.4 Energy and Nutrient Flow 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
Food chain: A series of organisms through which energy is transferred in the form of food grass toad snake producer primary consumer secondary consumer tertiary consumer grasshopper It illustrates the feeding relationships among organisms. A food chain always begins with a producer.

18.4 Energy and Nutrient Flow Trophic Level Trophic level: Each level or organism in a food chain grass toad snake producer primary consumer secondary consumer tertiary consumer grasshopper Note: The reason why food chains do not have more than four trophic levels because energy is lost at each trophic level. Only about 10% of the energy from one trophic level is transferred to the next level. Slides 37 and 38 will cover this concept. Generally, food chains do not have more than four trophic levels.

18.4 Energy and Nutrient Flow Food Web Food web: Interlinked food chains green plant caterpillar grasshopper aphid spider ladybird bird Note: Click on the Video-URL button to be directed to a website where a 2-minute video on the characteristics of a food web can be found. The video will help students revise what has been learnt on slides The video explains the terms producers, consumers, decomposers, food chain, and food web. Information about food chains can be represented using ecological pyramids. The next few slides discuss ecological pyramids. URL

18.4 Energy and Nutrient Flow 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. Use the diagram to illustrate the points: Grass and algae convert light energy into chemical energy. This energy is passed on to the other organisms (i.e. shrimps, grasshoppers, birds, fish and humans) through feeding.

18.4 Energy and Nutrient Flow Non-cyclic Energy Flow in an Ecosystem The flow of energy in an ecosystem is non-cyclic. Energy is lost to the environment as heat as it flows through the ecosystem.

18.5 Ecological Pyramids Learning Outcome
After this section, you should be able to: describe and interpret pyramids of numbers, biomass and energy.

18.5 Ecological Pyramids Ecological pyramids Pyramid of numbers
Pyramid of biomass Pyramid of energy Note: There are three types of ecological pyramids. Each one will be described in the following slides. Ecological pyramids can be used to compare the trophic levels of a food chain.

18.5 Ecological Pyramids Pyramid of Numbers
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 hawks (10) trophic level 4 trophic level 3 snakes (300) trophic level 2 rabbits (4 500) trophic level 1 grass plants ( )

18.5 Ecological Pyramids Pyramid of Biomass
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 hawks (5 kg) Note: The dry mass of an organism refers to the mass of the organism when it has been completely dried (i.e. all the water molecules have been removed from the organism). snakes (50 kg) rabbits (500 kg) grass (5000 kg)

18.5 Ecological Pyramids 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. Note: An example of a food chain that would result in an inverted pyramid of numbers: tree  aphids  parasitic protozoa Although the pyramid of numbers is inverted, the pyramid of biomass for the same food chain would not be inverted. This is because the tree would have a relatively much larger dry mass than all the aphids, and the dry mass of all the parasitic protozoa would be lower than that of the all the aphids. An example of a food chain that would result in an oddly shaped pyramid of biomass: phytoplankton  zooplankton  small fish  large fish The total dry mass of phytoplankton at time X may be smaller than the total dry mass of the zooplankton at time X, because the phytoplankton have a high reproductive rate and are able to replace the eaten phytoplankton quickly. The only ecological pyramid that will always be pyramid-shaped is the pyramid of energy. A pyramid of biomass can be oddly shaped if: organisms in one trophic level have a high reproductive rate.

18.5 Ecological Pyramids Pyramid of Energy
Represents the total energy in each trophic level of a food chain over a certain period of time hawks (10 kJ) tertiary consumer secondary consumer snakes (100 kJ) primary consumer rabbits (1 000 kJ) producers grass plants ( kJ)

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.

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. Hawks (10 k J) Energy lost Snakes (100 kJ) Ask students to deduce whether a short food chain or a long food chain would be more efficient in energy transfer. Answer: Short food chain; the shorter the food chain, the larger the amount of energy that reaches the final consumer, and the lesser the amount of energy lost to the environment. Rabbits (1 000 kJ) Grass (10 000kJ)

Nutrient Cycling in an Ecosystem
18.6 Nutrient Cycling in an Ecosystem Learning Outcome After this section, you should be able to: describe how carbon is cycled within an ecosystem.

18.6 Nutrient Cycling in an Ecosystem 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.

Watch the following video on the carbon cycle.
18.6 Nutrient Cycling in an Ecosystem Mini activity Watch the following video on the carbon cycle. List the various biological processes involved in the cycling of carbon as explained by Cole. URL Note: Click on the Video-URL button to be directed to a website where a 3-minute animation on the carbon cycle can be found. Let students watch this video as an introduction on the carbon cycle. The animation states that: respiration, decomposition, and burning release carbon dioxide into the environment, photosynthesis removed carbon dioxide from the environment circulation within water bodies can release/remove carbon dioxide into/from the environment, deforestation reduces the amount of plants available to remove carbon dioxide from the environment, Increased carbon dioxide in the environment leads to global warming. The animation states that plants breathe in carbon dioxide. This technically wrong since breathing is a process that involves the lungs, and plants do not have lungs. Gaseous exchange in plants takes place at the stomata. While, plants take in carbon dioxide when carrying out photosynthesis, they also release carbon dioxide during respiration.

Carbon dioxide is removed from the environment via:
18.6 Nutrient Cycling in an Ecosystem The carbon cycle Carbon dioxide is removed from the environment via: Photosynthesis Green plants absorb carbon dioxide from the atmosphere and use it to produce carbon compounds. Feeding Fossil fuel Note: Feeding transfers the carbon compounds from one organism to another. Dead plants and animals may form fossil fuels that are rich in carbon compounds. When animals feed on green plants, the carbon compounds become part of their bodies. Carbon compounds may be preserved as fossil fuels (e.g. coal, natural gas and oil)

18.6 Nutrient Cycling in an Ecosystem The Carbon Cycle photosynthesis feeding death Use this slide to help student recall information from the previous slide. This diagram shows the flow of carbon from the environment into plants and animals.

Carbon dioxide is released into the environment via:
18.6 Nutrient Cycling in an Ecosystem The Carbon Cycle Carbon dioxide is released into the environment via: Respiration Combustion Decomposition Carbon compounds such as glucose are broken down into carbon dioxide. The 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.

18.6 Nutrient Cycling in an Ecosystem The Carbon Cycle respiration death respiration death Use this slide to help student recall information from the previous slide. This diagram shows the processes by which carbon from plants, animals and fossil fuels, are released into the environment. decomposition combustion

18.6 Nutrient Cycling in an Ecosystem The Carbon Cycle respiration photosynthesis feeding death respiration death Use this slide to help students recall the whole carbon cycle. Process that removes carbon dioxide from the environment: Photosynthesis Process by which carbon is transferred from one organism to another: Feeding Process by which carbon is locked up in the environment for long periods of time: Fossilisation Process by which carbon dioxide is released into the environment: Respiration, decomposition, combustion decomposition combustion

18.7 Carbon Sinks Learning Outcome
After this section, you should be able to: 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.

18.7 Carbon Sinks 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.

Forests as carbon sinks
18.7 Carbon Sinks 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.

Chapter 18 Ecology

CHAPTER 18 Ecology.

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CHAPTER 18 Ecology.

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