Chapter 9 - Ecology Flashcards
0
Q
What is ecology’s aim?
A
To explain why organisms live where they do. Hence why ecologists study ecosystems.
1
Q
What is ecology?
A
The study of inter-relationships between organisms and their environments.
2
Q
What are ecosystems?
A
Is the ecological system based in the relationship between all the living organisms and the non living component of the environment within which they occur naturally.
3
Q
What is a population?
A
The number of individuals of a particular species that inhabit a particular region at the same time and which can interbreed.
4
Q
What is a habitat?
A
The physical or abiotic part of an ecosystem. A defined area with specific characteristics where the organism live. Eg oak forest, deep sea, sand dunes, rocky shores, garden pond.
5
Q
What is a microhabitat?
A
The climate which immediately affects an organism. This may be different from the general climate. Eg underneath a rotting log is the microclimate of wood louse.
6
Q
What is a niche?
A
The sum of the characteristics that determine the position of an organism in its ecosystem, this includes the chemical, physical, spatial and temporal factors required for the survival of a species and which limits it’s distribution and growth.
7
Q
How many species can occupy the same niche?
A
A niche is characteristic of a species and no 2 species occupy the same niche in the same environment in the same time.
However, a different species may occupy the same niche in the absence of the normal occupant.
8
Q
What is a biosphere?
A
The part of the earth, including volume of air, land and water that is capable of supporting life.
Life on the biosphere depends on the suns energy, on the circulation of heat and on essential nutrients.
9
Q
What is a biome?
A
A large ecosystem characterised by similar vegetation, animals and climate. It is characterised by a dominant type of plant that will then affect the type of fauna living in the habitat.
The biomes abiotic (non-living) factors, such as light intensity, wind, soil quality, amount of rainfall, temperature and nutrients, determine what koans and animals inhabit the zone.
10
Q
What are biotic factors?
A
Any living or biological factor.
11
Q
What are abiotic factors?
A
Any non-living or physical factors.
12
Q
What does one find in an ecosystem?
A
Numerous interaction populations. Living in communities and inhabiting particular niches of the habitat.
13
Q
What is a species?
A
A group of organisms that can successfully interbreed.
14
Q
What is a population?
A
Members of the same species living in one habitat.
15
Q
What is a community?
A
The living or biotic part of an ecosystem. All the organisms of all the different species living in one habitat.
16
Q
How can ecosystems be classified?
A
According to their vegetation.
17
Q
What are the major ecosystems in Malta?
A
Woodland (big trees - Oak, Pine) Buskett.
Maquis (small trees, large shrubs, climbers, olive tree, ivy)
Garigue develops in limestone areas. (Tough, low shrubs- thyme)
Steppe (herbaceous plants - grasses, leguminous plants)
Sand dunes (Ramla l-hamra) some distance inland from beach.
18
Q
What are food chains or food webs?
A
The many relationships between the members of a community in an ecosystem.
19
Q
What is each stage in a food chain referred to as?
A
Trophic level.
20
Q
What do the arrows represent in a food chain/web?
A
The flow of energy and matter through it.
21
Q
How are food chains organised usually?
A
Producers -> Primary Consumers (herbivores) -> Secondary Consumers (carnivores) -> Tertiary Consumers (top carnivores)
22
Q
The food chain begins with producers. What are they usually?
A
Plants, algae, plankton, and photosynthetic bacteria.
23
Q
Why are producers important and also usually found in the bottom of a food chain?
A
This is because uniquely producers are able to extract both energy and matter from the abiotic environment (energy from the sun and 98% if their matter from carbon dioxide in the air, with the remaining 2% from water and minerals in soil).
All other living organisms get both their energy and matter by eating other organism.
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Give an example of a food chain.
Cabbage plant -> caterpillar -> sparrow -> hawk.
| Algae -> water snail -> fish -> bear.
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What is a consumer?
An animal that eats other organisms.
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What are herbivores?
A consumer that feeds exclusively on plants. Primary consumers.
Eg: rabbits and sheep.
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What are carnivores?
A consumer that feeds exclusively on other animals. Secondary consumer.
Eg: Hedgehog and Geckos.
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What is the top carnivore?
A consumer at the too of a food chain, with no predators.
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What are omnivores?
A consumer that eats both plants and animals.
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What is a vegetarian?
A human that chooses not to eat animals (since humans are omnivores)
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What are autotrophs?
An organism that manufactures it's own food through photosynthesis. Producers.
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What are heterotrophs?
An organism that obtains it's energy and mass from other organisms. (Consumers and decomposers)
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What are plankton?
Microscopic marine organisms.
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What are phytoplankton?
Plant plankton. Microscopic marine producers.
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What are zooplankton?
Animal plankton. Microscopic marine consumers.
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What is a predator?
An animal that hunts and kills animals for food.
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What is prey?
An animal that is hunted and killed for food.
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What are scavengers?
An animal that eats dead animals, but doesn't kill them.
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What is detritus?
Dead and waste matter that is not eaten by consumers.
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What are decomposers?
An organism that consumes detritus. (Detrivores and saprophytes)
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What are detrivores?
An organism that eats detritus.
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What are saprophytes?
A microbe (bacterium or fungus) that lives on detritus.
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What is symbiosis?
Organisms living together in a close relationship. (Parasitism, mutualism and pathogen)
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What is mutualism?
Two organism living together for mutual benefit. One of them usually gets food from the other.
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What is commensalism?
Relationship in which only one organism benefits, while the other gains nothing but is not harmed.
Eg: Fish living in close vicinity of sharks, to get scraps of food which may fall while the shark is eating.
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What is a parasite?
An organism that feeds on a larger living host organism, harming it.
Eg: Tapeworm.
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What is a pathogen?
A microbe that causes a disease.
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What are heterotrophs also called?
Holozoic.
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What are autotrophs also called?
Holophytic.
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3 things can happen to the energy taken in by the organisms in a tropic level. What are they?
1) Energy can move on: it can be passed on to the biomass of the next tropic level in the food chain when the organism is eaten.
2) Eaten by detrivores: can become stored in detritus when the organism dies. This energy is passed on to decomposers when it decays.
3) Changed into heat energy: by inefficient chemical reactions, radiating warm bodies, or in friction due to movement. The heat energy is lost to the surrounding and cannot be regained by living organisms.
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How does energy enter the ecosystem?
As sunlight.
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What is the percentage used by plants to photosynthesis?
1%, the rest is lost in either transpiration, reflection or heat.
The total fixed energy by photosynthesis is called net primary production.
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What is the energy that is available to heterotrophs in the form of biomass called?
Net primary production.
54
When primary consumers eat plants, how much energy do they obtain?
10% as chemical energy.
| Plants lose 90% energy in growth, heat, respiration.
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At each trophic level, how much energy is available to them from the previous trophic level?
Only 10% of the energy (which is converted to biomass) is available to the consumer from the previous trophic level.
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How is so much energy lost in each trophic level?
Energy is lost due to egestion, excretion, in edible food, movement, growth and mostly as heat through respiration.
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What occurs once an organism dies?
It becomes food for the decomposes. The last of the energy is extracted and lost as heat.
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Which transfer of energy is most effective?
From primary consumer to secondary consumer, since a greater proportion of animal flesh is digested and absorbed.
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Which is the least effective energy transfer?
From producer to its consumer.
| The exception is plankton. Since they transfer 90%.
60
With efficient energy transfers in mind, why do we not just consume plants if they hold higher energy levels?
Although it is true that plant products yield a higher amount of protein, much more efficiently and cheaply then animal. Eg: Soya beans.
However since most plants contain cellulose, which we cannot digest, we in turn eat the consumers since they convert it into digestible products. Eg: cattle eating grass.
61
In general what occurs, once you go up a food pyramid?
The size of the individual increases, but the number of individual decreases.
62
There are 3 types of food pyramids. Mention them.
Pyramid of numbers (amount of organisms at each level)
Pyramids of biomass (how much they weigh at each level)
Pyramids of energy (how much energy there is in each level)
63
What is the basic premise of a food pyramid?
It shows us how much energy floes into each trophic level in a given time, hence the units are KJ.
Pyramids of energy are always pyramidal (energy cannot be created) and always very shallow, since the transfer of energy from one trophic level to the next is very inefficient. The missing energy, is lost as heat.
64
Energy is not recycled. But are inorganic nutrients?
Yes they are.
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How does matter cycle?
Between the biotic environment and in the abiotic environment.
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What happens to inorganic molecules in the matter cycles?
Simple inorganic molecules (CO2 & N2) are assimilated or fixed from the abiotic environment by producers and microbes, and built into complex organic molecules (such as carbohydrates, proteins & lipids).
These organism molecules are passed through food chains and eventually returned to the abiotic environment again as simple inorganic molecules by decomposers.
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What is quint essential for matter cycles?
Producers and decomposers, without which there would be no nutrient cycling and no life.
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What are simple inorganic molecules usually referred to as?
Nutrients.
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How can nutrients be grouped?
Major nutrients: molecules containing the elements C, H & O. (99% of biomass)
Macronutrients: includes molecules containing elements such as N, S, P, K, Ca and Mg. (Comprising of 0.5% of biomass)
Micronutrients or trace elements: (0.1 of biomass)
70
What are macronutrients and micronutrients collectively called.
Minerals.
71
While the major nutrients are obviously needed in the largest amounts. What also is needed?
The growth of producers is usually limited by the availability of minerals such as nitrate and phosphate.
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What are detrivores, in detail?
Animals that eat detritus. Eg: wood lice and earthworms. They digest most of the material but like all animals are unable to digest the cellulose and lignin in plant cell walls.
They break such plant tissue into much smaller pierces with a larger surface area, making it more accessible to the saprophytes.
Also assist the saprophytes by excreting useful minerals such as urea.
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What are saprophytes in detail?
Microbes (fungi and bacteria) that live on detritus. They digest if by extra cellular digestion and them absorb the soluble nutrients.
Given time, they can completely break down any organic matter (including cellulose and lignin) to inorganic matter such as carbon dioxide, water and mineral ions.
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In the carbon cycles, is there simply just one cycle going on or multiple ones?
Many carbon cycles present with time scales ranging from minutes to millions of years. However, Microbes play the major role in all stages.
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How is carbon fixed?
By microscopic marine producers mainly (algae and phytoplankton) from CO2 dissolve in the oceans.
Some is also done by terrestrial plants from CO2 in air.
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What is carbon fixation? How is this done?
It involves the reduction of carbon dioxide to larger organic molecules.
It is done by photosynthesis and chemosynthesis.
77
During Earth's early history, something important happen which had to do with photosynthetic bacteria. What happened exactly?
Photosynthetic bacteria called Cyanobacteria changed the composition of the Earths atmosphere by fixing most of the CO2 and replacing it with oxygen.
This allows the first heterotrophic cells to use oxygen in respiration.
78
What are Carboniferous rocks? How are they formed?
They come in the form of chalk, limestone and coral.
They are formed when a large amount of the fixed carbon is used by marine zooplankton to make calcium carbonate shells, which are not eaten by consumers and cannot be easily decomposed.
99% of the Earths carbon is in this form.
79
Why are decomposers important in the carbon cycle?
They are almost all microbes such as fungi and bacteria.
Most of the detritus is in the form of cellulose and other plant fibres, which eukaryotes cannot digest. Only a few bacteria posses the cellulose enzyme required to break down plant fibres.
Herbivorous animals such as does and termites depend on these bacterias in their guts.
80
How were fossil fuels made? Also what effect has using these fossil fuels left us with?
Much of the CO2 that was fixed by ferns during the Carboniferous era, was sedimented and turned into fossil fuels.
The recent mining and burning of fossil fuels has significantly altered the carbon cycle by releasing the carbon again. Causing a 15% increase in the CO2 in just 200 years.m
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What are involved in most of the stages in the nitrogen cycle?
Microbes.
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What is nitrogen fixation?
This process reduces nitrogen from the rhizosphere (soil atmosphere) to ammonium ions.
83
Explain nitrogen fixation in detail.
78% of the atmosphere is nitrogen gas, but this is inert and cannot be used by plants or animals. Nitrogen fixing bacteria reduce nitrogen gas to ammonia, which dissolves to form ammonium ions. This process uses the enzyme nitrogenase and ATP as a source of energy.
The nitrogen fixing bacteria may be free living in soil or water, or they may live in colonies inside the cells of roots nodules if leguminous plants such as clover or peas.
84
Nitrogen fixing bacteria may live in the root nodules of leguminous plants. What is this an example of?
Mutualism, as the plant gain a source of useful nitrogen from the bacteria, while the bacteria gain carbohydrates and protection from the plant.
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How else can nitrogen be fixed other than nitrogen fixing bacteria?
It can also be fixed to ammonia by humans using the Haber process and s small amount of nitrogen is fixed to nitrate by lightning.
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What is nitrification?
Nitrifying bacteria can oxidise ammonia to nitrate in 2 stages:
First forming nitrate ions NH4 (ammonia) and NO2 (nitrite) and then forming NO2 (nitrite) and NO3 (nitrate).
These are chemosynthesis bacteria, which means they use the energy released by nitrification to live, instead of using respiration.
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What is the only form of nitrogen that plants can take up?
Nitrate.
88
What is denitrification?
The anaerobic denitrifying bacteria convert nitrate to N2 and NOx, which is then lost to the air.
This represents a constant loss of useful nitrogen from soil, and explains why nitrogen fixation by the nitrifying bacteria and fertilisers are so important,
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What is ammonification?
Microbial saprophytes break down proteins in detritus to form ammonia in 2 stages:
First they digest proteins to amino acids using extra cellular protease enzymes.
Then they remove the amino groups from amino acids using deaminase enzyme.
90
What is the growth curve? In terms of population growth.
When a specie is introduced into a new environment, it's population grows in a characteristic way. This growth curve is often seen experimentally. Eg bees in a hive, bacteria in culture.
The curve is called a logistic or sigmoid growth curve.
91
The growth curve has 3 phases, with different factors being responsibly for the shape of each phase. Mention them.
Eg: rabbits in a field who reproduce sexually.
1) Lag phase: Little growth due to small population. Individuals may rarely meet, so few matings, king gestation so few births.
2) Rapid growth phase: Rapid growth, though not exponential. Few liming factors since relatively low density.
3) Stable phase: Slow growth due to intrados cues competition for food/territory, predation.
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What is the carrying capacity? In terms of population growth.
At the end of phase 3, the stable phase in the growth curve, the population is stable.
It is the maximum population supported by a particular ecosystem.
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What factors affect a population size?
Abiotic factors, seasons, food supply, interspecific competition, intraspecific competition, predation and parasitism & disease.
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How do abiotic factors affect a population size?
The population is obviously affected by the abiotic factors such as temperature, water, humidity, pH, light/shade, mineral supply, current, topography (altitude, slope, aspect), catastrophes (floods, fires) & pollution.
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How do harsh environments affect population size versus mild environments.
In harsh environments only a few species will have successfully adapted to the commission so they will not have much competition from other species.
However, in mild environments lots of different species could live there, so there will be competition.
In other words, in harsh environments abiotic factors govern who survive. While in mild environments biotic factors (competition) govern who survive.
96
How do seasons affect population size?
Many abiotic factors vary with the seasons, and this can cause a periodic oscillation in the population size.
Generally, the warmer the weather, the more reproduction and population increases.
This is only seen in species with a short life span. Such as insects.
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How does food supply affect population size?
A population depends on the amount of food supply. If there is plenty of food, the population increases and vice versa.
Eg: Red deer introduced to an Alaskan Island at first showed a population increase, but this large population grazed the vegetation too quickly for the slow growth to recover. So the food supply dwindled and the deer population crashed.
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Ow does interspecific competition affect population size?
This is competition for resources (food, space, water, light) between members of different species. And in general one species will out compete another one.
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How does intraspecific competition affect population size?
This is competition for resources between members of the same species. This is more significant than interspecific competition, since members of the same species have the same niche and so compete for exactly the same resources.
Intraspecific competition tends to have a stabilising influence on population size. If the population gets too big, intraspecific population increases, so the population falls again. If the population gets too small, intraspecific population decreases, to the population increases again.
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What is intraspecific competition also the driving force behind?
Natural selection.
Since the individuals with the best genes are more likely to win the competition and pass on their genes.
Some species use aggressive behaviour to minimize real competition. Ritual fights, displays, threat exposure are used to allow some individuals to reproduce and exclude others. This avoids real fights or shortages, and results in optimum size of population.
101
How does predation affect population size?
Population of predators and their prey depend on each other, so they tend to show cyclical changes.
This has been famously measured by populations of lynx and hares in Canada. If the population of the prey increases, the predator will have more food, so it's population will start to increase. This means that more prey will be eaten, so it's population will decrease, causing a cycle in both populations.
102
What makes a good predator?
1) Some hunt in packs. Work together to catch prey and share it.
2) Attacking the prey that is young, sick, old or injured. These prey are easier to overpower and kill. Also removes weaker individuals in prey population.
3) Catching large praying means that there is more food for the predator per kill.
4) By not depending on one particular species of prey. If the numbers go down, the predator can switch to another prey specie.
5) Migrating to areas where the prey is more plentiful.
6) Camouflage helps conceal the predator. Eg: the angler fish.
103
What helps a prey to escape its predator?
1) Some try to run, swim or fly faster than the predator.
2) By staying in large groups like herds of antelope. Many pairs of eyes can look out for predators. In case of danger, animals can give out calls to warn others in the group. Also if all the group starts running this might confuse the predator. Eg school of fish.
3) Some animals taste horrible. Making them less attractive as meat.
4) Other animals like bees or wasps can sting the predator.
5) Some have warning colour. Telling the predator to keep clear. Eg South American poison arrow frog.
6) Some prey mimic other animals possessing an advantage that might help them avoid predation. Eg: hoverflies look like wasps.
7) Camouflage helps to hide prey. Many tend to blend it with their surroundings. Eg: the flounder fish.
8) Some prey try shock tactics to startle a would be predator. Eg when attacked the bombardier bettle sprays a hot toxic brew.
104
How do parasitises and diseases affect a population size?
Parasites and their hosts have a close symbiotic relationship. So their populations also oscillate.
This is demonstrated by winter moth caterpillars (host) and wasp larvae (parasites). If the population of parasites increases, they kill their host, so their population decreases. This means there are fewer hosts for the parasites, so their population decreases.
Allowing for both to recover.
A similar pattern happens in pathogens and their hosts.
105
How have humans impacted their environment?
The huge increase in human population over the last hundred years has been possibly due to the development of intensive farming, including monoculture, selective breeding, huge farms, mechanisation and the use of chemical fertilisers and pesticides.
However, this intense environment is damaging our environment and is becoming increasingly difficult to sustain.
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What is organic farming?
Farmers turning to environmentally friendly options. Due to intensive farming.
107
What is monoculture?
Until middle 29th century farms were usually small and mixed (they grew a variety of crops and kept animals). About 1/3 of the population worked on farms.
Today the picture is quite different, with large uninterrupted areas of one colour due to specialisation in one crop - monoculture.
It increases the productivity of farmland by growing only the best variety of crops. Allowing more than one crop per year. Simplifying sowing and harvesting of the from reducing labour costs.
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How do monocultures impact the environment?
1 )Using a single variety of crop reduces genetic diversity and renders all crops in a region susceptible to disease.
2) Fertilisers are required to maintain soil fertility. This is expensive and can pollute surrounding groundwater due to leaching.
3) Pesticides are required to keep crops healthy. Again this is expensive and potentially polluting.
4) Reduces species diversity, causing several effects. Such as allowing a pest species to get out of control.
5) Less attractive countryside.
109
What is an alternative to monoculture?
Some farmers are returning to traditional crop rotations, where different crops are grown in a field each year.
This breaks the life cycles of pests (since host is always changing), improves soil texture (since different crops have different root structures and methods of cultivation) and can increase soil nitrogen.
110
Why are fertilisers used?
Since the rate of plant growth is usually limited by the availability of mineral ions in the soil, then adding more of these ions as fertilisers is a simple way to improve fields.
This is a keystone of intensive farming.
The most commonly used fertilisers are soluble inorganic fertilisers containing nitrate, phosphate and potassium ions.
111
Are inorganic fertilisers good effective?
They are very effective, but also have undesirable effects of the environment.
Since nitrate and ammonium ions are very soluble, they do not remain in the soul for long and are quickly leached out, ending up in local rivers and lakes, causing eutrophication.
112
Is there an alternative for fertilisers?
Yes, organic fertilisers which cause less harm to the environment. Eg animal manure, composted vegetable matter, crop residues, and sewage sludge.
These contain the main elements found in inorganic fertilisers, but in organic compounds such as urea, cellulose, lipids and organic acids.
113
Since plants can only take up inorganic materials. How are organic fertilisers effective?
Plants cannot make use of these organic materials in the soil, their roots can only take up inorganic material ions such as nitrate, phosphate and potassium.
But the organic compounds can be digested by soil organisms such as animals, fungi and bacteria, who then release inorganic ions that plants can use.
114
What are some advantages to using organic fertilisers?
1) Since they are organic, they are less soluble. The inorganic minerals are released slower as they are decomposed. Preventing leaching.
2) Organic wastes need to be disposed of anyways, so they are cheap. Furthermore, spreading it on fields, meanings it will not be dumped in landfills. Where they may have caused uncontrollable leaching.
3) organic material improves soil structure by binding soil particles together and provides food for soil organism such as earthworms. Improving drainage.
115
What are some disadvantages of organic fertilisers?
They are bulky and less concentrated in minerals than inorganic fertilisers, so more needs to be spread.
They may contain unwanted substances such as weed seeds, fungal spores, heavy metals. Also very smelly!
116
What are pesticides?
To farmers, a pest is any organism (animal, plant or microbe) that damages their crops. Some form of pest control has always been needed, whether it is chemical (pesticides), biological (predators), or cultural (weeding or scarecrow).
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What are the different types of chemical pesticides?
Herbicides: Anti-plant Chemicals.
Insecticides: Anti-Insect Chemicals.
Fungicides: Anti-fungal chemicals.
Bactericides: Anti-bacterial chemicals.
118
How do pesticides work?
They have to be effective against the pest, but have no effect on the crops. They may kill the pests or just reduce their population by slowing growth or preventing prediction.
Intensive farming depends completely on pesticides. Some crops are treated with 18 different chemicals to combat a variety of weeds, fungi and insects.
In addition by controlling pests that carry human disease,they have saved millions of human lives.
119
What disadvantages occur from using pesticides?
Persistence: refers to how long a pesticide remains active in the environment. Some chemicals are broken down by decomposers in the soil (biodegradable) and so are not persistent. Others cannot be broken down by microbes (non biodegradable) and continue to act for many years, these are persistent pesticides. Which did a great deal of damage to the environments.
Bioaccumulation: refers to the built up of a chemical through food chain. Non biodegradable pesticides are not soluble in water and is not excreted easily, so it remains in the fat tissue of animals.
As each consumer eats a large mass of the trophic level below it, it accumulates in the fat tissue of animals at the top of the chain.
120
What is eutrophication?
Refers to the effect of nutrients on aquatic ecosystems. These naturally profess from being oligotrophic (clean water with few nutrients and algae) to eutrophic (murky water with many nutrients and plants) and occasionally hypertrophic (a swamp with a mass of lands and detritus)
In the context if pollution eutrophication has come to mean a sudden and dramatic increase in nutrients due to human activity, which disturbs and eventually destroys the food chain.
121
How can we measure eutrophication?
By Biochemical Oxygen Demand. This measures the rate if oxygen consumption by a sample of water, and therefore gives a good indication.
High level = lots of organic material and aerobic microbes. Eg: eutrophication.
