Energy And Matter In Ecosystems

Question 1

Energy

Answer 1

The capacity to cause change, particularly to do work

Question 2

Energy source

Answer 2

The sun provides most of earths energy in a form of electromagnetic radiation that is known as as solar energy

Question 3

A biogeographical cycle

Answer 3

Refers to the pathway of matter through the living components (organisms) and non-living components (such as soil, rocks, water and the atmosphere) of an ecosystem

Question 4

A geochemical cycle

Answer 4

Refers to the chemical interactions that exist in crustal and subcrustal reservoirs, such as the deep earth and lithosphere (crust)

Question 5

Biotic components of an ecosystem

Answer 5

Light energy enters an ecosystem via producers (plants and algae)
All organisms rely on producers either directly or indirectly
Energy is stored in chemical bonds in the organic compounds and is released when the chemical bonds are broken

Question 6

Photosynthesis

Answer 6

Carbon dioxide + water —> glucose + oxygen
Only producers perform photosynthesis

Question 7

Biomass

Answer 7

The chemical energy stored in plants as organic matter can be measured
Is the total mass of biological matter (living or dead) in a given area

Question 8

Photosynthesis efficiency

Answer 8

How well a producer converts light energy into carbohydrates during photosynthesis

Question 9

Net primary productivity (NPP)

Answer 9

Is the remaining amount of energy that is available to consumers
Net production = gross production - energy used in respiration

Question 10

Consumers (1)

Answer 10

An organisms that depends on other organisms for its nutrients and energy requirements
They extract energy stored in chemical bonds by a process called cellular respiration

Question 11

Cellular respiration

Answer 11

Is a metabolic process. It is the breakdown of organic matter in order to release energy
Glucose + oxygen —> carbon dioxide + water (+ energy in the form of ATP)
Both producers and consumers perform cellular respiration

Question 12

Food chains and food webs

Answer 12

Are examples of qualitative, predictive models that allow ecologists to monitor raw sustainability of feeding relationships in an ecosystem
The position an organism occupies in a food chain or web is called its trophic level

Question 13

A generalised food chain

Answer 13

Sunlight - producer - primary consumer (herbivore) - secondary consumer (second-order consumer) - tertiary consumer (third-order consumer) - top carnivore (apex predator)

Question 14

A food web

Answer 14

Is a group of food chains that are linked together, showing the interactions between food chains within a community
Plants are autotrophs: they make their own food by transforming light energy from the sun during photosynthesis

Question 15

Process of energy through food chain

Answer 15

• potential energy stored in plants
• primary consumers (herbivores) feed on producers (plants)
• carnivores and omnivores are secondary consumers
• secondary consumers feed on primary consumers
• at each trophic level in the chain, a proportion of the available energy is used during essential biological processes and lost due to inefficiencies during transfer. Some energy is lost from the food chain as chemical energy in organic wastes of dead plant and animal tissues, collectively called detritus
• energy from the top consumers is transferred to scavengers and detritivores.
  Scavengers are animals that feed no the dead remains of other animals.
  Detritivores feed on the detritus and help speed up the process of decay by breaking it down into smaller pieces.
  Decomposes continue this process, returning these nutrients to the soil or water

Question 16

Energy loss in food chains

Answer 16

Progressively less energy is available at each tropic level as you move up a food chain
On average 10% of the energy at one trophic level is passed on to the next level
The remaining 90% is lost to the surroundings as heat energy and chemical energy in wastes
The efficiency of energy transfer can vary from less than 0.1% to well over 10%

Question 17

Trophic efficiency

Answer 17

The percentage of the energy at one trophic level that is transferred to the next trophic level

Question 18

Pyramids of numbers

Answer 18

In which the size of each tier is proportional to the number of individuals parent at each trophic level
A typical food chain tends to have a drop in the number of organisms at each tropic level. This is represented as a pyramid or numbers. Pyramids or numbers may not always have an apex representing high trophies levels.
E.g. a single very large producer, such as a eucalyptus tree, may support a large number of primary consumers.
In these cases, an inverted pyramid of numbers results. Inverted pyramids of numbers can also result when communities contain parasites.

Question 19

Food webs are integrated food chains

Answer 19

Most species depend on more than one kind of organisms for their food. A herbivore as a primary consumer will feed on number of species of plants and, in turn, will be earth by several different kinds of carnivores
The feature that distinguishes a food chain from a food web is that an organism can occupy different trophic levels in different food chains. In other words food webs represent the dynamic interactions between organisms in an ecosystem
Humans are omnivorous consumers, humans can obtain more of the energy available in plants, because they are not exposed to the energy losses that occur by eating foods higher up the food chain. When humans consume livestock, they only obtain 1% of the total energy that is available in producers. Members of populations of different species move in and out of different ecosystems, so an organism may be part of one food chain or we at one time but not at another time

Question 20

Pyramids of biomass

Answer 20

Each tier represents the total dry weight of organisms at each tropic level
A pyramid of biomass is another type of ecological pyramid that can be constructed for a community. Pyramid of biomass records the total mass of (amount of dry organic matter) of organisms at each level. Measurements can be made at one particular time or thy can be calculated as rates (productivity) from measurement of dry mass in a given area for the duration of a year (e.g. g m -2 year -1)
Almost always pyramidal in shape, certain circumstances may give an inverted pyramid

Question 21

Pyramids of energy

Answer 21

The size of each tier is proportional to the production (e.g. in kJ) of each trophic level
Although pyramids of numbers and biomass provide ecologists with useful information, to get fuller understanding of what happened to energy transfer in communities, pyramids of energy aer constructed.
Pyramids of energy are expressed in units of energy per area in a given time. They show the rate at which energy is transferred from one trophies level to another. Pyramids of energy allow ecologists to describe the rate of energy transfer in a community . This allows them to make predictions about weather a community can be sustained and hat impact any changes to rates of energy transfer will have on the community.
Pyramids of energy can never be inverted in the way that pyramids of numbers or biomass sometimes are

Question 22

Drawing pyramids of energy

Answer 22

1. The bottom level should always represent a producer
   
   2. Subsequent levels should be labelled primary consumer, secondary consumer and tertiary consumer
   3. As far as possible, each trophic level should be drawn to scale. Unless you have alternative data, measure one-tenth the length of the preceding trophic level (this represents the average energy transfer efficiency of 10%)
   4. Use labelled arrows to indicate energy leaving each trophic level in the form of heat

Question 23

Biogeochemical cycle of matter

Answer 23

Important difference between energy and matter is that the sun provides a constant, external supply of energy, while the total matter is a fixed resource and therefore matter must be recycled

Question 24

Producers

Answer 24

Also called autotrophs, include green plants
Green pigment, chlorophyll enables plants to trap energy from sun during photosynthesis
Energy is used in combining carbon dioxide and water to produce food and oxygen, which becomes available to the consumers in the community

Question 25

Consumers (2)

Answer 25

Also called heterotrophs take in nutrients originally produced by plants as food
Most of nutrients are returned to communities as faeces and urine, or when the consumer dies

Question 26

Types of consumers

Answer 26

Herbivores - eat only plants
Carnivores - eat animals
Omnivores - eat both plants and animals
Detritivores - eat dead matter (plants and animals)

Question 27

Detritivores vs decomposers

Answer 27

Detritivores scavenge waste products or dead bodies while decomposers break down (decomposers) leaf litter and other living an non-living material

Question 28

Energy in ecosystems

Answer 28

Green plants, algae, and some bacteria use the suns energy to produce glucose in a process called photosynthesis
The chemical energy stored in glucose fuels all the processes in the cell, called metabolism
- the photosynthesis that occurs is vital to life on earth, providing oxygen and absorbing carbon dioxide
- cellular respiration is the process by which organisms break down energy rick in molecules (e.g. glucose) to real ease the energy in useable form (ATP)

Question 29

Photosynthesis efficiency

Answer 29

How well a producer converts light energy into carbohydrates during photosynthesis
This depends on the:
- amount of light
- temperature
- availability of raw materials

Question 30

Why is energy so important?

Answer 30

Organisms need energy to survive
Consumers obtain matter and energy from producers
Uses of energy
- synthesis - making proteins
- growth and repair - cell divisions and making new tissues
- reproduction - develop and growth offspring
- temperature maintenance for warm blood animals
- top perform work - move muscles, heart beat
- cellular processes - nerves impulses, cell transport

Question 31

Carbon exists in the non-living environment as:

Answer 31

• Carbon dioxide (CO2)
• Carbonic acid (HCO3-)
• Carbonate rocks (limestone and coral = CaCO3)
• Methane (CH4)
• Deposits of Fossil fuels
• Dead organic matter

Question 32

Carbon is released into the atmosphere by

Answer 32

• respiration by plants and animals
• Decay of animal and plant matter
• Combustion of organic material
• The ocean releases CO2 into the atmosphere
• Geological activity

Question 33

Carbon is taken from the atmosphere by:

Answer 33

• photosynthesis
• The oceans where the sea water becomes cooler, more CO2 dissolves and become carbonic acid
• In the upper ocean areas organisms convert reduced carbon to tissues or carbonates

Question 34

Carbon cycle

Answer 34

When organisms eat plants, they take in the carbon and some of it becomes part of their own bodies
When plants and animals die, most of this bodies are decomposed and carbon atoms are returned to the atmosphere
Plants and animals are also constantly adding carbon back to the atmosphere through respiration

Some dead plants and animals are not decomposed fully and end up in deposits underground (oil, coal, etc)
Carbon in rocks and underground deposits is released very slowly into the atmosphere. This process takes many years
Additional carbon is stored in the ocean. Carbon readily diffuses in and out of water. Many animals pull carbon from water to use in shells, etc
Animals die and carbon substance are deposited at the bottom of the ocean
Oceans contain Earths largest store of carbon

Question 35

Human impact on the carbon cycle

Answer 35

Fossil fuels ( coal, oil, gas) release carbon stores very slowly
However burning anything releases more carbon into atmosphere - especially fossil fuels
• increased carbon dioxide in atmosphere increases global warming
• Fewer plants mean less CO2 removed from atmosphere

Question 36

Why is nitrogen so important?

Answer 36

Nitrogen makes up 78% of our atmosphere
Nitrogen is an essential component of DNA, RNA and proteins
Nitrogen is a limiting factor for plant growth. Not enough or too much means plants cannot survive

Question 37

Bacteria play an important role in the nitrogen cycle-

Answer 37

• nitrogen-fixing bacteria are able to fix atmospheric nitrogen
• Nitrifying bacteria convert ammonia to nitrite, and nitrite to nitrate
• Denitrifying bacteria return fixed nitrogen to the atmosphere

Question 38

Nitrogen cycle

Answer 38

Atmospheric fixation also occurs as a result of lightning discharges
Humans intervene in the nitrogen cycle by producing and applying nitrogen fertilisers

The ability of some bacterial species to fix atmospheric nitrogen or convert it between states is important to agriculture

Nitrifying bacteria include nitrosomas and nitrobacter. These bacteria convert ammonia to forms of nitrogen available to plants (nitrates)

Nitrogen must be the ground to enter food chains. Nitrogen-fixing bacteria and lightning and nitrogen to the soil
Plants rake up the nitrogen from the ground. Animals then consume the nitrogen from the plants
Nitrogen is returned to the soil and atmospheric by the action of bacteria on dead organic matter

Question 39

Human impact in nitrogen cycle

Answer 39

Combustion
Commercial fertilisers
Removal of nitrogen from soil when mined
Discharge of sewage

Question 40

Decomposers

Answer 40

Includes saprophytic fungi and microscopic bacteria which break down the dead plant and animal material and return it to the soil as nutrients
- are crucial in the cycling of nutrients within an ecosystem
- prevent the accumulation of dead plant and animal material
- are also a food source themselves for many consumers