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Biology - Unit 3 > Populations > Flashcards

Populations Flashcards

1
Q

Define ecosystem

A

The community of organisms and non-loving components of an area and their interactions
Vary from very large to very small (microhabitat)

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2
Q

Describe biotic and abiotic factors, giving examples

A

Biotic = living features of an ecosystem e.g. disease, parasitism, predators
Abiotic = non=living features of an ecosystem e.g. light, temperature

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3
Q

Define community

A

All of the population of different species living together in a habitat.

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4
Q

What is a habitat?

A

The region where an organism normally lives

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5
Q

Define population

A

A group of organisms of a single species interbreeding and occupying a particular area

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6
Q

What are the factors affecting population size?

A
  • Birth rate
  • Death rate
  • Immigration
  • Emigration
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7
Q

What are strategies for population growth ?

A

Introducing Fugitive Species and equilibrium species

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8
Q

Define fugitive species

A

Cannot tolerate competition, to increase numbers they reproduce rapidly and have effective dispersal mechanisms e.g weeds

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9
Q

Define equilibrium species

A

Control their own population by competition with a stable habitat. usual pattern of growth is a sigmoid curve called a one step growth curve e.g. bacteria and rabbits

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10
Q

Explain the phases of population growth in a bacterial population

A

Lag = bacteria adjusts to their nee environments and prepare for growth by synthesising enzymes
Exponential = Bacteria cells replicate exponentially, with no limiting factors
Stationary = Bacteria growth levels off as cell death equals the number of more cells produced by cell division.
Death = cell death exceeds cell division. Nutrients are now depleted and waste products reach toxic levels

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11
Q

Define niche

A

Describes how an organism ‘fits’ into an ecosystem and its role in that environment

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12
Q

Define birth rate and death rate

A

Birth rate - the number of offspring born per thousand of population per year
Death rate - the number of deaths per thousand of population per year

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13
Q

What is emigration?

A

The number of individuals leaving a region per thousand of population per year

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14
Q

When do population sizes increase ?

A

When births and immigration are greater than deaths and emigration

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15
Q

When do population sizes decrease?

A

When deaths and emigration are greater than births and immigrants

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16
Q

What is carrying capacity?

A

The maximum population size of species that an environment can sustain
Variety depending on biotic and abiotic factors

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17
Q

Describe density-dependent and density- independent factors, giving examples

A

Density - dependent factors = factors whose effects on population size differ with population density e.g. competition, predation, disease
Density- independent factors = factors whose effects on population size differ remain the same same regardless of population density e.g. climate

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18
Q

What is intraspecific competition?

A

The same species competing for the same source

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19
Q

What is interspecific competition?

A

Competition between members of different species

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20
Q

What is abundance?

A

The number of individuals per species in a specific area at any given time

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21
Q

What is random sampling?

A

Technique used to avoid bias
Eg. Creating coordinates from a random generator

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22
Q

What is a trophic level?

A

The position that an organism holds in a food chain, food web or pyramid

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23
Q

Why is some energy never taken in at each trophic level?

A
  • Some parts of food aren’t consumed
  • Some are indigestible
  • Plants can’t use all light energy (need specific wavelengths )
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24
Q

How is energy lost at each trophic level?

A

respiration, lost as heat

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25
How can you measure abundance in animals ?
Capture- mark-recapture technique. - Organisms trapped or caught n day 1 are marked and then released. The same sampling technique is used on day . The use the rolling to determine population size Number on day1 x Number of day 2 ————————————————— Number in sample 2 which are marked Kick Sampling - In a stream and counting freshwater invertebrates
26
How would you calculate abundance in organisms such as plants?
Random Sampling = using quadrat to find the density of organisms in a given area Systematic Sampling = using transects to determine changes in percentage cover of a species due to changes in abiotic factors e.g light intensity
27
What is a producer?
Autotrophic organism which absorbs light energy to convert simple inorganic compounds into more complex organic compounds, such as carbohydrates
28
Define consumers
Heterotrophic organisms which cannot fix carbon from inorganic sources
29
Define detritivores
Feed on dead organic matter
30
Define decomposers
Bacteria or fungi Break down organic compounds into simpler inorganic compounds, which are soluble and can be absorbed by plant roots
31
How would you calculate the photosynthetic efficiency ?
Quantity of light energy incorporated into biomass ————————————————————————. X 100 Quantity of light energy hitting the leaf
32
What is gross primary productivity ?
The rate of production of chemical energy in biological molecules by photosynthesis per unit area and time.
33
What is Net Primary Production?
The energy in plant biomass which could pass to the primary consumers at trophic level 2 during feeding.
34
Wha is secondary transfer?
The rate at which heterotrophs accumulate energy in the form of new cells and tissues. Heterotrophs cannot fix carbon from inorganic sources like the producers do - they must ingest or absorb organic carbon from other organisms.
35
Will herbivores or carnivores have a lower secondary productivity, why?
Herbivore As carnivores are more efficient at energy conversion then herbivores. A carnivores protein rich diet is more readily and efficiently digested and less energy is lost as waste.
36
How do you calculate the efficiency of energy transfer ?
Energy incorporated into biomass after transfer ——————————————————————- X 100 Energy available before transfer
37
How are ecological pyramids used/ displayed?
Food chains can be represented by these The base is always the primary consumers at trophic level 1 The consumer at the end of the food chain will always be at the apex of the pyramid
38
What is a pyramid of biomass?
The mass of biological tissue and content within e.g. carbs, lipids and proteins Not all biomass is available to the next trophic level (bones, beaks ) therefore the energy they contain is not transferred These may look inverted as no account is taken of reproductive rate or longevity.
39
What is succession ?
A sequence of changes, in the composition of a community over time. A succession will eventually lead to a stable climax community, which has high biodiversity and highly productive.
40
What each stages of succession called?
A sere
41
Describe primary succession
- Begins from bare rock or the recent sight of a volcanic eruption. The first organism to colonise the rock are the pioneer species (lichens, mosses and algae) - Pioneer species change the rock surface by penetrating it and allowing humus (which retains water ) to accumulate, allowing grasses and ferns to colonise the area - These further change the rock as their roots penetrate deeper and further. Death and decay over several generations allows more soil to accumulate and other high plant species invade - As the community becomes more diverse other organisms take advantage of the new habitat and food sources. Eventually a climax community is established until the environment changes again
42
What is an example of a climax community?
a woodland
43
What is secondary succession?
- Begins from bare soil, a climax community will be achieved much faster as the soil is already present and it may contain viable bulbs, seeds and spores. - Bare soil can be exposed after a wildfire - Human activity may prevent a climax community being achieved
44
What are some examples of human activity which prevent a climax community in secondary succession?
- Grazing sheep - Heather moorland management by controlled burning - Farming of land - Deforestation and soil erosion
45
Describe the key steps of the carbon cycle
1) Carbon dioxide from the atmosphere is fixed into carbohydrate by the light independent stage of photosynthesis 2) Respiration, in plants and animals, releases carbon dioxide into the atmosphere due to the action of decarboxylase in the link reaction and Krebs cycle 3) Combustion of fossil fuels releases carbon, in the form of carbon dioxide, into the atmosphere 4) Microorganisms responsible for decay (decomposers) release carbon dioxide into the atmosphere due to respiration 5) Carbon fixed into organic molecules by producers pass from trophic level to trophic level along food chains during feeding 6) Fossil fuels are formed, over millions of years, from the remains of dead plants and animals; anaerobic conditions inhibit decay and the carbon rich biological molecules become fossil fuels such as oil, coal and gas over time.
46
What human activity is disrupting the carbon cycle ?
- Deforestation (less carbon is fixed into carbs by photosynthesis) - Burning fossil fuels on a massive scale (more carbon is released due to combustion) - An increase in decomposition (more carbon is released due to decomposition e.g landfill sites)
47
What effects on biodiversity and agriculture come about due to the enhanced greenhouse effect (global warming) ?
- Melting polar ice caps and rising sea levels - Increased frequency of extreme weather - Increased desertification and soil erosion - Increased extinction rate - Changes in the distribution of disease vectors such as mosquitos
48
What is a carbon footprint?
Total amount of carbon dioxide produced directly due to the actions of an individual, product or service per year
49
How has agriculture got a carbon footprint ?
- The production of farming tools - The production of insecticides fungicides and fertilisers - Farm machinery , powered by fossil fuels - Transport of produce
50
What changes can be made in farming to reduce the carbon footprint?
Produce less meat = meat production requires more resources then crop production Crops should be grown for human consumption, not as animal feed Rice paddies produce methane, therefore alternatives should be found Packaging should be reduced to a minimum Transport distances should be reduced and more food produced locally
51
What is the nitrogen cycle ?
The flow of inorganic or organic nitrogen within the abiotic and biotic elements of an ecosystem
52
What is a nitrogen fixing microorganism ?
Fixing atmospheric nitrogen gas into ammonia and ammonium ions
53
What is nitrification ?
Converting the products of decay into nitrate ions
54
What is azotobacter bacteria?
Free-living bacterium found in soil. It is aerobic and fixes nitrogen gas into ammonium ions
55
What is Rhizobium bacteria?
Found in the root nodules of legumes and shares a symbiotic relationship with them. Uses the enzyme nitrogenase to fix nitrogen gas into soluble ammonium. Nitrogenase activity is inhibited by oxygen, therefore the root nodules surround the bacteria with a layer of leghaemoglobin.
56
What is nitrification ?
Microorganisms, namely bacteria, convert ammonium into nitrite and then nitrate
57
Nitrosomas bacteria
Free living Aerobic bacteria Converts ammonium into nitrites
58
Nitrobacter bacteria
Free living aerobic bacteria Converts nitrites into nitrates which is then absorbed into plant root hair cells by active transport
59
What is denitrification ?
The loss of soluble nitrate compounds from the soil under anaerobic conditions. Converts nitrate back to atmospheric nitrogen
60
How do farmers try to avoid denitrification ?
Ploughing the fields Mixes the oxygen and soil together to inhibit the denitrifying bacteria, pseudonomas and promote growth of nitrogen fixing bacteria
61
62
Describe the stages of the nitrogen cycle
1) Decomposers (bacteria & fungi) break down large organic molecules in the plant remains into inorganic ammonium; this is putrifaction / decay 2) Nitrosomas converts ammonia into nitrites, then nitrobacter converts nitrite into nitrates; nitrifcation 3)Inrganic nitrogen sources are converted into nitrogen gas by pseudomonas: denitrification 4) azobacter and rhizobium fix free nitrogen gas into ammonium and nitrates ; nitrogen fixing 5) Nitrates are absorbed by root hair cells via AT, requiring ATP and has high oxygen demands
63
64
How can human activity improve available soluble nitrate?
- Adding chemical fertilisers - Adding manure - Adding treated sewage - Planting legume such as clover - Ploughing o improve aeration
65
Describe eutrophication
Chemical fertilises, manure and slurry are washed into waterways if used in excess and cause an increase of algae and plant growth.
66
What occurs if algal bloom develops as a result of eutrophication ?
Covers the waters surface, blocking light into lower depths meaning photosynthesis cannot take place.
67

Biology - Unit 3 (11 decks)

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