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Biology IGCSE > Chapter #18 - Organisms And Their Enviornment > Flashcards

Chapter #18 - Organisms And Their Enviornment Flashcards

1
Q

Ecology

A

the study of organisms in their environment.

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2
Q

Do organisms live in isolation of each other?

A

Organisms do not live in isolation of each other. They live in an environment with many other organisms.

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3
Q

Habitat

A

The place where an organism lives

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4
Q

Population

A

A group of organisms of the same species, living in the same area at the same time.

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5
Q

Community

A

All of the populations of all of the different species in an ecosystem.

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6
Q

Ecosystem

A

A unit containing all of the organisms in a community and their environment, interacting together.

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7
Q

Niche

A

the role of an organism in its natural environment. The wayinwhich it interacts with other organisms and with the non-living partsofthe environment.

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8
Q

What do organisms do in an ecosystem?

A

In an ecosystem, each organism has a role.

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9
Q

Where does all the energy in an ecosystem originate from?

A
  • The sun
  • Sunlight energy is captured by plants and turned into glucose/starch/otherbiological molecules
  • Animals get their energy by eating plants
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10
Q

Food chain

A

A diagram showing the flow of energy from one organism to the next, starting with a producer

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11
Q

Producer

A

An organism that makes its own organic nutrients (usually using energy from sunlight, through photosynthesis).

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12
Q

Consumer

A

An organism that gets its nutrients by feeding on other organisms.

Primary – secondary – tertiary – quaternary… etc

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13
Q

Food web

A

a network of interconnected food chains.

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14
Q

Which way do the arrows point in a food web?

A

In the direction of the energy flow

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15
Q

How much energy is transferred between trophic levels?

A

About 10% of the previous trphic level’s energy gets transferred.

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16
Q

How does biomass change across trophic levels?

A

There is less biomass the higher the tropic level. This is because only about 10% energy of the previous trophic leves are passed on.

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17
Q

Trophic level

A

Position of an organism in a food chain/web or pyramid.

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18
Q

Herbivore

A

an animal that gets its energy by eating other plants.

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19
Q

Carnivore

A

an animal that gets its energy by eating other animals.

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20
Q

Decomposer

A

an organism that gets its energy from dead or waste organic material.

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21
Q

How is energy lost as it is passes through a food web?

A
  • Heat loss from respiration
  • Not all parts of the organism are eaten e.g. roots and bones not being eaten
  • Not all parts of the organism being eaten is absorbed. When an animal eats another,its digestiveenzymes break downmost of the nutrients,but not all. Some are not digested or absorbed and are just removed as faeces. (Faeces contain energy, but it is lost from that food web.
  • Not all organisms are eaten so they may die and they are decomposed.
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22
Q

Pyramid of numbers

A

a graph showing the total number of individual organisms at each level in the food chain of an ecosystem.

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23
Q

What happens to the number of organisms at different positions in a food chain?

A

There are usually more plants than animals and more herbivores than carnivores in a food chain.

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24
Q

How can we represent the number of organisms at different positions in a food chain?

A

We can represent the number of organisms using a pyramid of numbers.

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25
Why is there less energy available as you go up the pyramid of energy?
There is less energy available as you go up the pyramid because some energy is lost to the environment.
26
Why are there fewer animals at higher levels of the pyramid of energy?
There are fewer animals higher up the pyramid because less energy is available at each level.
27
What are the problems with pyramid sof numbers?
* Many organisms feed at more than one trophic level. Eg – you are a primary consumer when you eat vegetables, a secondary consumer when you eat meat / drink milk, and a tertiary consumer when you eat a predator fish e.g. salmon. * Doesn't represent the complexity of food webs
28
Pyramid of biomass 
a graph showing the relative quantity of biomass at each trophic level.
29
Why are pyramids of biomass better than pyramids of numbers?
Because pyramids of biomass give a better idea about the quantity of energy at each trophic level than pyramids of numbers.
30
Pyramid of Energy 
a graph showing the relative quantity of energy at each trophic level
31
How could scientists calculate the figures for a pyramid of energy?
1. Work out all the links in the food web 2. Take samples of each organism and find out how much energy they contain. (Kill the organism, dry it, burn it to see how much energy is released) 3. Multiply by the number of each organism in that food web
32
Why are pyramids of biomass often used instead of more accurate energy measurements?
Because the data is much easier to collect.
33
Where is the most energy in a food chain?
At the start of the food chain.
34
Why is there more energy at the start of the food chain?
There is more energy at the start of the food chain because less energy has been "lost" between the trophic levels.
35
What type of food provides humans with the most efficient energy and why?
Humans can get the most efficient energy from plant foods like wheat, rice, and potatoes because there is more energy at the start of the food chain. Less has been "lost" between the trophic levels.
36
37
Species
A group of organisms that can reproduce to produce fertile offspring.
38
Population
A group of organisms of one species, living in the same area at the same time.
39
Do population sizes **ususally** change?
Most populations stay roughly the same size over many years. They may fluctuate, but the average will stay the same.
40
What factors impact population size?
Overall: Population size depends on how many individuals leave and enter it. * Individuals leave when they die, or migrate to another population * Individuals enter when they are born or migrate into the population However... Usually births and deaths are more important than immigration and emigration.
41
Populations increase if...
birth rate is greater than death rate/death rate is less than birth rate
42
Populations decrease if...
death rate is greater than birth rate/birth rate is less than death rate
43
Populations remain the same if...
birth rate and death rate are equal
44
Sigmund growth curve
S-shaped curve showing the change in population size
45
Label the different parts of this graph
46
What occurs throughout the lag phase
The population remains small as it grows slowly (adjusting to conditions, and few individuals to reproduce).
47
Exponential phase/log phase
The population grows at a maximum rate. Birth rate exceeds death rate.
48
What occurs throughout the stationary phase?
The population remains roughly constant. Birth rate and death rate are roughly equal.
49
What occurs throughout the death phase?
The final stage of a population growth curve. The population falls. Death rate exceeds birth rate.
50
What are the limiting factors in a population and when are present?
In the log phase, nothing is slowing the growth down but the capacity to reproduce. From the stationary phase some environmental factors become limiting factors - they limit the population growth, even if everything else would allow it to increase.
51
What could the limiting factors be in a population?
Possible limiting factors: Food supply? Build up of waste toxins such as ethanol? In other cases... Number of predators Competition for food Disease Space Weather?
52
What is the main point for preadator-prey relationships?
fluctuations in the population of prey species can lead to similar fluctuations in predator populations.
53
What do age pyramids represent?
the number of individuals in different age groups at one point in time – usually for a whole country
54
What does the following age pyramid represent?
**An increasing population.** If all the younger organisms in this population grow up and reproduce, the population will increase.
55
What does the following age pyramid represent?
**A stable population.** The size of younger age groups are similar to the size of older age groups. So the population should not change much.
56
What is the human popuation overall
It is increasing. Bottom heavy age pyramid Increasing population size
57
How rapidly is the human population increasing?
The human population size is increasing rapidly – about 9000 extra people every hour.
58
Why has the human population increased for the last 300 years?
* Reduction in disease * Improved water supply, sewage treatment, food hygiene, standards of hygiene. * Immunisation * Antibiotics * Increase in food supply
59
Decomposers
feed on organic waste material from plants and animals and on their dead bodies. Eg. Many fungi and bacteria.
60
Whay are decomposers important?
Because they release substances from dead organisms, including: * carbon * nitrogen
61
Why is the carbon cycle important?
Carbon is very important because C atoms are part of all biological molecules (carbs, fats, proteins).
62
What are the steps of the carbon cycle?
A) 0.04% of air is carbon dioxide. B) During photosynthesis, C atoms from CO2 become part of glucose and starch molecules in the plant. C) Some glucose is used in respiration by the plants and becomes part of CO2 again in the air. D) Some of the carbon-containing molecules in the plant will be eaten by animals. E) Animals respire, releasing C back into the air as CO2 F) Decomposers feed on waste materials like urine and faeces G) Decomposers respire, released some C back into the air as CO2 H) Some waste products and dead bodies that are not decomposed get buried in sediments. Over a long period of time they turn into fossil fuels (coal, oil, or natural gas). I) When fossil fuels are burnt = combustion = the C in them combines with the O in the air and CO2 is therefore released into the air again.
63
How is crabon dioxide stored?
* In the air * As glucose in animals plants, ad decomposers to use for respiration * In waste in dead bodies
64
How is carbon dioxide released?
* Combustion of fossil fuels * Decomposers respire * Plants respire * (molecules containing carbon are eatedn by anumals) animals respire
65
Why do living things need nitrogen?
* To make proteins * To make DNA
66
How much of air is made up of N?
* 78% * A molecule of nitrogen gas is made up of 2 N atoms (N2) * They are inert molecules = will not readily react with other substances
67
Nitrogen fixation
converting inert N2 into a more reactive form. For example ammonia (NH3) or nitrates (NO3-)
68
Why must nitrogen fixation occur?
The nitrogen in the air is in such an unreactive form that it cannot be used by plants and animals at all. Nitrogen in the air must be changed into a more reactive form, like ammonia (NH3) or nitrates (NO3-)
69
What are the different ways nitrogen fixation can happen?
* lightning * artificial fertilizers * nitrogen-fixing bacteria
70
How does nitrogen fixation happen through lightning?
Lightning makes some nitrogen gas in the air combine with oxygen, forming nitrogen oxides. They dissolve in rain and then get washed into soil where they form nitrates.
71
How does nitrogen fixation happen though arteficial fertilisers?
Nitrogen and hydrogen can be made to react in an industrial chemical process that forms ammonia. Ammonia is used to make ammonium compounds and nitrates, which are sold as fertilisers.
72
How does notrogen fixation happen through nitrogen-fixing bacteria?
These bacteria live in the soil, or in root nodules (swellings) on plants like peas, beans and clover. They use N gas from the air spaces in the soil and combine with other substances to make ammonium ions and others.
73
What is the nitrogen cycle?

Biology IGCSE (21 decks)

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