1
Q
Ecology meaning
A
is the study of the various interactions between living things (organisms) and their environment.
2
Q
An ecosystem refers to
A
organisms and their interactions with their environment.
3
Q
The biosphere is
A
the part of the planet inhabited by organisms.
4
Q
A habitat is
A
where an organism lives
5
Q
Environment
A
All external factors that influence living things are referred to as its environment.
6
Q
Environmental factors affecting organisms:
A
Abiotic factors are non-living factors (these include edaphic factors which relate to the soil) that aftect organisms.
Biotic factors are living factors which affect organisms.
Climatic factors refer to weather conditions over a long period of time that affect organisms.
7
Q
Abiotic factors
A
non-living factors (these include edaphic factors
8
Q
Biotic factors
A
Biotic factors are living factors which affect organisms.
9
Q
Climatic factors
A
Climatic factors refer to weather conditions over a long period of time that affect organisms.
10
Q
Aspect effect on organisms
A
The direction an ecosystem faces. In the northern hemisphere, southern-facing slopes get more sun.
Eg. Sun-seeking plants tend to grow on south-facing slopes.
11
Q
Exposure
A
The extent to which organisms are vulnerable to the environment eg. exposure to wind
Eg Strong winds can disrupt plant root contacts in the soil
12
Q
Steepness
A
Steep slopes lose water quickly & soils are washed away.
Eg
Conifers can grow on steep slopes as leaves retain water.
13
Q
Altitude
A
Height above sea level.
Higher altitudes are cooler and have decreased oxygen availability.
Eg
Some plants eg. mosses and animals eg. birds are adapted to living at high altitudes.
14
Q
Currents
A
Plants and animals can be washed away to various locations.
Eg seaweed attached to rocks
15
Q
Edaphic: clay soil
A
Small particles leaving little room for air and water to pass through
Eg few plants and animals thrive here due to lack of available oxygen and water and the difficulty penetrating the soil
16
Q
Sandy soil
A
Large particles leaving lots of room for oxygen and water.
However, since water passes through easily, nutrients are.
quickly washed out.
Eg plants with long roots grow well in sandy soil as it is easily penetrable
17
Q
Organic matter (humus)
A
Humus provides nutrients, binds soil particles and helps retain water and minerals.
Eg
Provides food to earthworms.
Plants grow here due to the abundance of nutrients.
18
Q
Soil ph
A
The degree of acidity or alkalinity of the soil.
Different plants are adapted to different soil pH eg.
heather grows in acidic soils, lavender grows in alkaline soils. Most plants grow best
in neutral (pH = 7) soil.
19
Q
Air content
A
Provides oxygen for organisms.
Eg
Oxygen is required for aerobic respiration of plants and animals. Lack of oxygen stunts growth and can lead to death.
20
Q
Mineral content
A
Can influence soil pH. Plants require certain minerals for survival eg. magnesium for photosynthesis.
Eg high water content can lead to minerals being washed out of the soil which can effect soil ph. If there are insuffficient minerals present plants cannot grow
21
Q
Water content
A
Water in the soil is absorbed by plant roots
Eg
Plants need water for
photosynthesis and for general transport of nutrients and minerals.
22
Q
Biotic: humans
A
Human activity can both positively and negatively impact ecosystems.
Eg
Pollution harms the ecosystem. Conservation parks can improve and maintain biodiversity.
23
Q
Pollination and seed dispersal
A
Plants often depend on other organisms to reproduce
Eg
Flowers attract insects with bright colours the pollen sticks to the insect, and when the insect flies away it disperses the pollen to other flowers. Animals can disperse seeds by eating the plants and excreting its seeds.
24
Q
Competition
A
A struggle for a limited resource eg. territory, water
Example
Plants compete with each other for light, animals compete with each other for food.
25
Parasitism
Parasites weaken their hosts and may reduce their numbers.
Eg
Fleas infect foxes & rats.
26
Predation
Certain species survive by killing and eating other species.
Eg
The rabbit population may be controlled by the fox population killing and eating them for survival.
27
Food
The availability of food determines how many organisms can survive.
Eg
If there is an abundance of plants available, many herbivores will survive. If there is an abundance of herbivores, predators will survive by eating them.
28
Climatic: light intensity
Light is required for photosynthesis
Eg
Trees grow tall to get more light. Plants grow in the areas that receive the most light.
29
Day length
Affects plant flowering & germination, as well as migration & hibernation in animals
Eg
Most plants in the northern hemisphere grow better during the spring and summer when the days are longer as there is more sunlight and hence more energy for photosynthesis.
30
Temperature
Influences growth rates of organisms, hibernation and migration patterns.
Eg
Bears hibernate in the winter to avoid the cold season.
31
Wind strength
Can cause physical damage to plants eg. effects root attachment to the soil.
Increases evaporation.
Eg
Trees grow better on the sheltered side of the slope
32
Salinity
Controls the movement of water by osmosis
Eg
If the external environment is high in salt, water will move out of the organism into the environment (principle behind salting food to kill bacteria)
33
Humidity
Amount of water Vapor in the air
Influences the evaporation of in the air
from the soil and from plant stomata. If there is high humidity, water cannot evaporate.
34
Rainfall
Water is essential for metabolism, transport and photosynthesis.
If there is too much rainfall soils can become waterlogged and drained of nutrients, which will inhibit plant growth and hence animal survival. If there is not enough rainfall, plants will be unable to survive.
35
Factors affecting aquatic ecosystems:
Waves can cause damage to organisms, which influences how animals adapt e.g. barnacles have tough outer shells.
Currents can transport warm and cold water to a habitat, which can impact certain organisms' abilities to survive there.
Light can only penetrate the upper layers of bodies of water. As plants need light for photosynthesis, most aquatic plants are found in the upper layers of water. Since organisms feed off plants, they are also usually found in the upper layers.
The salinity of the water influences the movement of water in and out of organisms.
Freshwater amoeba have a contractile vacuole for osmoregulation
36
Energy flow
The sun is the main source of energy for the planet, and energy flows in one direction. Sun -
Producers > Consumers.
• Producers are organisms that carry out photosynthesis. This includes all plants (autotrophic).
Consumers are organisms that take in food from another organism. This includes all animals. Primary consumers feed on producers, secondary consumers feed on primary consumers, tertiary consumers feed on secondary consumers.
37
Tropic level
is a feeding stage in the food chain. Only 10% of the energy is passed onto the next trophic level, with the remaining 90% being used by the organism or lost as heat.
38
Grazing food chain
is a sequence of organisms in which each organism is eaten by the next member of the sequence (only one species at each trophic level).
39
A food web
contains two or more interlinked food chains (may be many species at one trophic level).
40
A pyramid of numbers
is a visual representation of the number of organisms at each trophic level in a food chain. A pyramid of numbers can be useful for comparing the number of organisms at each trophic level of different food chains.
41
Constructing a pyramid of numbers
•Consider the food chain: leaves -> beetle -> spider - blackbird
• The producer (leaves) will make up the base of the pyramid. There will be thousands of leaves, so this level is the biggest.
The primary consumer (beetles) will make up the next level of the pyramid.
The secondary consumer (spiders) will make up the next level of the pyramid.
The tertiary consumer (blackbird) will be the top level of the pyramid.
Remember that only 10% of energy is passed on between trophic levels. For this reason, the number of organisms will decrease as you go up with pyramid (if it is a normal pyramid.
42
Limitations of use
• The pyramid of numbers does not account for the size of the organism at each level, which can result in several different shapes of pyramid eg. an inverted pyramid.
• Consider the food chain: oak tree - squirrel + fox + flea
• Think of how many squirrels can live on a single oak tree. Even though the oak tree is huge, its numbers are small. The producer (the oak tree) makes up the base of this pyramid but it will be represented by a single line.
• The next level of the pyramid is the primary consumer, the squirrel. This level will be much bigger than the first level, since many squirrels can live on a single oak tree.
• The next level of the pyramid is the secondary consumer, the fox. There must be more squirrels than foxes, otherwise the foxes wouldn't survive, so this level is smaller than the second level.
• The final level of the pyramid represents fleas, a parasite. Think of how many fleas can live on a single fox. Therefore this level is going to be the biggest.
• Hence not every pyramid of numbers looks like a typical pyramid.
43
An ecological niche
is the role of an organism in its ecosystem.
44
Nutrient recycling
Nutrient recycling is the re-use of nutrients.
45
The Carbon Cycle:
• The carbon cycle refers to the way in which organisms take in and give out carbon to and from the environment.
Plants take in carbon dioxide when they carry out photosynthesis.
Plants give out carbon dioxide when they carry out respiration.
• Animals take in carbon from the environment when they eat plants.
Animals give out carbon dioxide when they carry out respiration.
When animals die, they are acted on by decomposers such as bacteria and fungi, which releases carbon dioxide into the environment.
Fossil fuels are made from decomposing plants and animals. When we burn fossil fuels eg.
coal, we are releasing carbon dioxide into the environment.
46
Nitrogen cycle
The Nitrogen Cycle:
•The function of the nitrogen cycle is to take nitrogen from the environment and make it available for organisms to use.
•Nitrogen gas in the air is converted to ammonia (NHs) and other nitrogenous compounds such as ammonium (NH*) or nitrate (NO;) by a process called nitrogen fixation. It is an anaerobic process that is mainly carried out by nitrogen-fixing bacteria in the soil or roots of plants such as legumes.
Nitrogen fixation can also occur as a result of lightning strikes, volcano eruptions and industrial processes (eg. the Haber process)
Nitrates are taken in (assimilated) by plants (and animals when they eat plants). The nitrates are converted into plant & animal amino acids which form proteins, and nucleic acids which form RNA and DNA
When plants or animals die, decomposition of the dead organisms is carried out by bacteria & fungi of decay, found in the soil. They release nitrogenous compounds such as ammonia (NHs) into the soil.
• Nitrification is the conversion of ammonia and ammonium (NH*) compounds into nitrite and then into nitrate. This is carried out by chemosynthetic, nitrifying bacteria in the soil.
Some of these nitrates are assimilated by plants from the soil, while some nitrates are acted upon by denitrifying bacteria.
Denitrification is the conversion of nitrates into nitrogen gas. This is an anaerobic process.
47
Human impact
Three ways in which humans affect environments are pollution, conservation and waste management
48
Pollution
Pollution is the addition of harmful substances to the environment.
Types include
domestic pollution (household waste),
agricultural pollution (insecticides, slurry)
and industrial pollution (chemical waste).
49
Pollutant
A pollutant is any harmful addition to the environment.
50
Chlorofluorocarbons
Chlorofluorocarbons (CFCs) are an example of a pollutant that contributes to air pollution.
CFCs are found in refrigerants, aerosols and foams.
Ozone is a gas that absorbs UV radiation from the sun before it gets to Earth. The ozone in the atmosphere around the earth is called the ozone layer.
CFCs weaken the ozone layer, which allows more UV radiation to reach earth.
UV radiation increases the risk of skin cancer and damages plants and animals.
We can help to maintain the ozone layer by reducing our consumption of CFCs.
CFCs are also being replaced by hydrofluorocarbons (HFCs) which do not damage the ozone layer.
51
Conservation
Conservation is the management of the environment to maintain biodiversity and prevent
exanction.
Conservation practices in fisheries:
• Using nets that are designed to allow young fish to escape. This prevents the catching of young fish, so that they have a chance to breed and allow the fish population levels to recover.
• Introduction of fishing quotas prevents over-fishing and ensures there are enough fish left in the sea to continue to breed and maintain the species.
52
Waste management
Waste Management refers to how we process and control our waste as a society.
Effective waste management aims to minimize pollution and maintain biodiversity.
In agriculture, slurry is stored in leak-proof pits and spread on dry land.
• In fisheries, waste parts of fish are neutralised, pulped, dried and recycled as fertiliser or pig feed.
In forestry, parts of trees not removed are allowed to decay and return nutrients to the soil, or they can be made into mulch for flowerbeds and paths.
53
Role of micro organisms
The role of micro-organisms in waste management
Micro-organisms break down organic waste in landfill sites.
Bacteria and fungi of decay are used in the secondary stage of sewage treatment to break down organic matter.
• The 3 stages of sewage treatment are:
• Primary - large particles and debris are removed by screening (passing through a mesh) and sedimentation (allowing particles to settle at the bottom)
o Secondary - bacteria and fungi breakdown and remove organic matter
o Tertiary - minerals are removed from the sewage.
54
Three rs
The amount of waste we produce can be reduced by the three Rs:
• Reduce consumption of unnecessary items e.g. only buy what you need
• Reuse items where possible e.g. wash and re-use plastic bottles/lunch containers
Recycle as much as possible e.g. glass, cans
55
A population
A population is all the organisms of the same species living in an area.
56
Community
A community is all the organisms living in an area. There are many species in a community.
57
Factors that control the numbers in a population
act mainly on the birth rates and death rates.
58
Factors controlling population size include
competition, predation, parasitism and symbiosis.
59
Competition
occurs when organisms struggle for a scarce resource.
60
Intra-specific competition
takes place between members of the same species.
61
Inter-specific competition
occurs between members of different species.
62
Contest competition is
when two organisms physically struggle for a scarce resource with the winner getting all of the resource and the loser getting none ('winner takes all').
63
Scramble competition
is when organisms struggle for a scarce resource and all organisms get some of the resource
64
Predation
is the hunting, killing and eating of another organism.
65
A predator
is an organism that hunts, kills and eats another organism.
66
A prey is
the organism that is eaten by the predator.
67
Predation
Predation usually increases the number of predators and decreases the amount of prey.
• The numbers of predators and prey often show repeated cycles of rising and falling numbers.
• The cyclical relationship is influenced by factors such as the availability of resources.
o If there is not enough space/food/water for the prey, it will die off and the predator will either have to migrate or find a new prey in order to survive. If there is plenty of space/food/water for the prey, the population will thrive, which will in turn provide plenty of food for the predator. This may cause the predator population to increase, which would subsequently decrease the prey population.
An example of predation is an owl predator) and a mouse (prey)
68
Parasitism
Parasitism occurs when an organism lives in or on another organism of a different species, feeding on it and causing harm.
69
Exoparasites
live on the outside of the host (eg. fleas living on dogs).
70
Endoparasites
live on the inside of the host (eg. worms living in the human intestine).
71
symbiosis
(when two organisms of different species live together and at least one benefits).
72
Mutualism
• Mutualism is a form of symbiosis that is separate to parasitism. In mutualism, two organisms of different species live together and both benefit. An example of mutualism is nitrogen-fixing bacteria in the roots of plants get anaerobic conditions from the plant, and the plant gets nitrates from the bacteria.
73
Population Dynamics
Factors affecting human population numbers include
War decreases the population due to death. However, there are often baby booms after wars that result in population increase.
• Famine reduces population numbers due to starvation resulting in death.
The use of contraception reduces the birth rate and rate of population growth.
• Disease decreases population numbers due to death. Improved disease control methods have reduced the death rate and caused an increase in human numbers since the 1900s.
74
Study of an ecosystem:plants
Buttercups, dandelions, ryegrass, daisies, clovers, bluebells, thistles.
75
Study of an ecosystem:animals
Earthworms, snails, spiders, rabbits, slugs, foxes, blackbirds, beetles.
76
The ecosystem is studied by carrying out the following steps:
Constructing a map of the ecosystem to be studied.
Identifying plants & animals using simple keys.
• Estimating the numbers of plants & animals by doing a quantitative study.
Measuring abiotic factors.
• Presenting the information collected in tables, diagrams, graphs and histograms.
77
Collection methods
Trowel/shovel
Dig into the soil
Earthworms, insects, plants
78
Collection methods
Tullgren funnel
The bulb heats the soil,
causing organisms in the soil to burrow down further. They fall out of the bottom and drop into the flask.
Worms, mites, insects
79
Collection methods
Beating trays
Shake hedges, bushes, trees
Ladybirds, beetles, spiders
80
Collection methods
Pooter
Place one tube near the
organism you want to capture, suck in through the other tube.
Insects, spiders
81
Collecting methods
Pitfall trap
Dig a space in the soil for the flask to fit so that the top of. the flask is level with the ground. Place two rocks on either side of the flask with a larger stone on top to keep rainwater out.
Crawling animals eg snails, slugs, insects.
82
Collecting methods
Place bait in the trap and
leave in the habitat. When the animal enters the trap, the door shuts behind it.
Field mouse
83
Collecting methods
Potassium Permanganate solution
Pour into soil
Earthworms
84
Collecting methods
Cryptozoic trap
Place the board on the ground overnight.
Organisms that prefer dark and damp conditions - slugs, worms, woodlice.
85
A qualitative study
determines if an organism is present or absent.
86
A quantitative study
records the numbers of organisms that are present.
This can be subjective (based on personal judgement. Not recommended as it is not reliable) or objective (the number of organisms is counted and measured using tools).
87
A quantitative study of plants involves using:
• Quadrats - a square made of wood or plastic.
88
Why is it randomly thrown
The quadrat must be randomly thrown in order to examine the grassland correctly. To ensure it is a random throw, throw a pen over your shoulder and then place the quadrat where the pen lands. (The reason the quadrat is not thrown over your shoulder is because this could be dangerous.
89
Quadrats are used for determining:
a) % cover of plants or slow-moving animals
• A grid square is used to calculate percentage cover. This is a quadrat that is further divided into smaller squares.
• When the guadrat is thrown randomly, identify how many times the organism you are examining (eg. clover) touches a grid point on the quadrat.
The percentage cover of an organism is calculated by dividing the number of grid points touched by the total number of grid points, and multiplying by 100 to make it a percentage.
b) % frequency
• A normal quadrat can be used for this.
• The quadrat is randomly thrown 10 times and the presence or absence of the organism in the quadrat is noted
• Frequency is calculated by dividing the number of quadrat throws the organism was present in by 10 (the total number of quadrat throws) and multiplying by 100 to get a percentage.
90
• Transects:
a Line transect. This a rope marked at regular intervals eg. 0.5m. Record the names of organisms (usually plants) that are touching the intervals.
b) Belt transect. This is like a row of quadrats. The plants found in each quadrat are recorded.
A quantitative study of animals in a habitat involves using the capture-recapture method.
Number = (C 1st x C 2nd) / M 2nd.
Where C 1st is the animals caught on the 1st visit.
C 2nd is animals caught in the 2nd visit.
M 2nd is the animals that were marked on the 2nd visit.
91
Errors may arise during the study of an ecosystem in the following ways:
Mistakes may be made in judgement, recording and calculating.
• There is a certain amount of randomness in the experiment eg. you might happen to throw your quadrat where there are very few organisms.
Conditions change in the ecosystem over time eg. weather.
• Habitats studied may not reflect the overall ecosystem.
92
Three abiotic factors are measured and their effects are related to the organisms that are present in the ecosystem:
Ecosystem
Grassland
93
Factor:
Equipment used:
Effect:
Soil water content
Digital soil meter and probe
If there is too much
water in the soil, the roots of plants can rot.
If there is not enough water, plants can't get sufficient nutrients from the soil.
94
Factor
Equipment used
Effect
Soil ph
pH meter with a
probe.
Certain plants favour
certain soil ph eg.
heather prefers acidic soils.
95
Factor
equipment used
Effect
Light intensity
Light meter (ensure there is even cloud cover on the day)
Plants eg. buttercups need sunlight for photosynthesis. They grow tend to grow in sunlit areas and avoid shaded areas.
96
An adaption is
any alteration that improves an organism's chance of survival and reproduction.
Adaptations may be structural, behavioural or competitive.
97
One example of a structural adaption
is that ladybirds are brightly coloured so they can be easily seen and avoided as they are full of formic acid.
98
• One example of a behavioural adaptation is
how thrushes smash snails against rocks to
break rhe shel
•
99
One example of a competitive adaptation is
how foxes hunt at night when other predators may not. (This is also a behavioural adaptation).
100
The results of a study of an ecosystem can be presented
in tables, lists, charts, graphs, diagrams, etc.
The results should include food chains, food webs and pyramids of numbers.
The work carried out should be presented in a portfolio.
101
Biotic factor
Living factor
102
Habitat
The place where an organism lives
103
Community
All of the different organisms living in an area
104
Population
All members of the same species living in an area
105
Niche
The functional role of an organism in an ecosystem
106
Biosphere
(f) The part of the Earth that sustains life
107
Qualitative survey
Checking for the presence or absence of an organism in an ecosystem
108
Organisms at the top of the food chain
(ii) Tertiary consumers
109
Why pyramid of numbers are constructed to one or two levels
Very little energy (10%) is transferred from one level in a food chain to the next one
110
Write notes on the following.
(i)
Factors which influence the size of the human population.
-Famine decreases the size of the human population.
-War decreases the size of the human population.
-An outbreak of a disease can decrease the size of the human population.
111
Organism adaptations.
.
Organisms have different adaptations in order to protect themselves from being preyed on and for survival.
-Organisms can have behavioural adaptations, e.g. birds migrate in the winter to protect themselves from adverse environmental conditions.
-Organisms can have physical adaptations, e.g. frogs have green-coloured skin so that they can blend in with their habitat and they are camouflaged so it is not easy for predators to see them.
112
(i Conservation.
-Conservation is the wise management of natural resources.
-Conservation is important in order to prevent the extinction of organisms
-An example of conservation in fisheries is using a large mesh size in order to allow small fish to
swim tree
113
Describe the steps you would take to estimate the size of the population of a particular animal species in the ecosystem you have studied.
Capture-recapture method
-On the first day, collect 30 snails.
-Mark them in a way that does not endanger them or make them more visible to predators
-Release the snails in the same place that you collected them in
-On the second day, collect 30 snails.
-Count how many of them are marked.
-The size of the population can be estimated using the following formula:
(Number caught and marked on the first day × number caught on the second day) + number marked on the second day
114
Name a plant from the ecosystem you have studied and indicate two abiotic conditions which favour its presence.
Ecosystem: woodland
Plant: daffodil
Factors: -Temperature
-Light intensity
115
How did you measure any one of the abiotic conditions mentioned in (il)?
Temperature: using a thermometer
Light intensity: using a lux meter
116
Why is it important that nutrients are recylcled in nature
They can be reused
117
During the nitrogen cycle, nitrogen from the air is converted to nitrates.
Of what benefit is this?
nitrogen cannot be used by plants, whereas nitrates can be absorbed by plants
118
Nitrates are formed directly from other molecules in the soil, Name one of these molecules.
Nitrite
119
Mention one role of animals, other than as consumers, in the nitrogen cycle.
excrete ammonia in urea / decompose to form nitrogen compounds
120
Name the family of plants which have a symbiotic relationship with nitrogen-fixing bacteria.
legumes
121
The nitrogen in the air is converted to nitrates but the percentage of nitrogen in the air does not change. What process is responsible for this?
denitrification
122
What is the role of modern fertilisers in the nitrogen cycle?
add usable nitrogen to the soil
123
Answer the following questions by reference to a named ecosystem which you have investigated.
Name of ecosystem:
Give one example of a possible error in ecological surveying
Surgest how this error might be minimised or eliminated.
Name of ecosystem: woodland
(i) miscounting of organisms
(ii) study the ecosystem a number of times and find the average number of organisms present
124
As part of your study you constructed a food web. In the space below or in your answer book, draw a food web from the ecosystem you named above, containing:
1. At least three food chains, and
2. At least four trophic levels.
Biology leaving Cert
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