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A2 Biology > 3.5 - Population size and Ecosystems > Flashcards

3.5 - Population size and Ecosystems Flashcards

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1
Q

Why are ecosystems described as being dynamic?

A
  • intensity of the energy flowing through varies
  • biological cycles vary mineral availability
  • habitats change over time as succession occurs
  • new species arrive and others leave
  • climate change continues to alter habitats
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2
Q

What 4 factors influence population size?

A
  • birthrate (natality)
  • deathrate (mortality)
  • immigration
  • emigration
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3
Q

What is the definition of population?

A

An interbreeding group of organisms of the same species occupying a particular habitat

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4
Q

What is the definition of birthrate?

A

The reproductive capacity of a population, the number of new individuals derived from reproduction per unit time

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5
Q

What is the definition of immigration?

A

The movement of individuals into a population of the same species

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6
Q

What is the definition of equilibrium species?

A

Species that control their population by competition rather than reproduction and dispersal

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7
Q

What are fugitive species?

A

Poor at competition, so instead rely on a large capacity for reproduction and dispersal to increase their numbers, they invade a new environment rapidly

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8
Q

What are the 4 phases of the sigmoid curve?

A
  • the lag phase
  • the exponential phase
  • the stationary phase
  • the death phase
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9
Q

What is the lag phase?

A
  • population does not increase but there is slow growth
  • period of adaptation or growth, intense metabolic activity
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10
Q

What is the exponential phase?

A
  • as numbers increase, as long as there’s no limiting factor, more individuals become available for reproduction
  • rate cannot be maintained due to environmental resistance (less food, conc of waste, not enough space)
  • for bacteria in a flask, limitting factors include food availability, overcrowding, competition
  • for biotic species, factors include predation, parasitism and disease, competition
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11
Q

What is the stationary phase?

A

-when birthrate is equal to the death rate
- the population reaches its maximum size, which is the carrying capacity for each particular environment

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12
Q

What is the death phase?

A
  • the factors that slow population growth at the end of a lag phase become more prominent
  • population size decreases until death rate is greater than birthrate and the graph has a negative gradient
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13
Q

What is the definition of environmental restistance?

A

Environmental factors that slow down population growth

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14
Q

What is the definition of biotic?

A

A part of the environment which is living.

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15
Q

What is the definition of abiotic?

A

A part if the environment which is non-living

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16
Q

What is the definition of carrying capacity?

A

The maximum number around which a population fluctuates in a given environment

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17
Q

What is the difference between a logarithmic growth curve and an exponential growth curve?

A
  • in exponential growth, the increase in numbers is larger with each unit of increasing time
  • in logarithmic growth, the increase in numbers is smaller with each unit of increasing time
  • an exponential growth curve is the inverse of logarithmic growth
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18
Q

What are density dependent factors?

A

Effect a greater proportion of the population when population is denser, biotic factors such as disease or lack of food

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19
Q

What are density independent factors?

A

The effect of abiotic factors in the environment does not not depend on population density, for example a flood or fire

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20
Q

How is population size controlled by negative feedback?

A
  • if the pop rises above the set point, a density dependant factor increases mortality or reduces breeding to such an extent that the population declines
    -if the pop falls below the set point, environmental resistance is temporarily relieved so that the population rises again
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21
Q

What is biogeography?

A

Study of species abundance and distribution

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22
Q

What is meant by the term abundance?

A

The number of individuals in a species in a given area or volume

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23
Q

What methods are used to measure animal abundance?

A

-capture-mark-recapture experiments, using the Lincoln index calculation
- kick sampling in a stream and counting aquatic invertabrates

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24
Q

What methods are used to measure plant abundance?

A
  • using a quadrat to calculate the mean number of individuals in several quadrats of a known area, to find the density
  • estimating percentage cover of plants in which individuals are hard to recognise
  • estimating percentage frequency
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25
Q

How is species distribution measured?

A
  • a line transect shows the organisms that lie on a line, at measured intervals
  • a belt transect shows the abundance data for a given area at measured distances along a transect
    *use of kite diagrams to record results
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26
Q

What are ecosystems?

A

A characteristic community of interdependent species interacting with the abiotic components of their habitat
- can be small, large, temporary or permanent

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27
Q

What is the definition of a habitat?

A

The place in which an organism lives

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28
Q

What is the definition of a community?

A

Interacting populations of 2 or more species in the same habitat at the same time

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29
Q

What are trophic levels?

A

Feeding levels; the number of times that energy has been transferred between the sun and successive organisms along a food chain

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30
Q

What is biomass?

A

The mass of biological material in living or recently living organisms

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31
Q

What is the primary energy source for any food chain?

A

Green plants, cyanobacteria and some protoctista are called producers because they incorporate the suns energy into carbohydrates which is used as food, and therefore the energy source for successive organisms in the food chain

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32
Q

What happens to energy as it goes along a food chain?

A

It decreases at each level, usually through heat.
This limits the size of food chains.

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33
Q

What is meant by decomposition?

A

When producers and consumers die, energy remains in the organic compounds of which they are made

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34
Q

What are saprobionts?

A

Organisms that derive energy and raw materials for growth from extracellular digestion of dead and or decaying material

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35
Q

What are detrivores?

A

Organisms like like earthworms, which feed on small fragments of organic debris. This is detrius, the remains of dead organisms and fallen leaves

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36
Q

What are decomposers?

A

Microbes such as bacteria and fungi that obtain nutrients from dead organisms and animal waste, they complete the process of decomposition started by detrivores

37
Q

What are the contributing factors that support longer foodchains?

A
  • more energy/light that enters at the first trophic level, the longer the chain can be
  • if energy transfer between trophics is efficient, more trophics benefit
  • predator and prey populations fluctuate, affecting food chain length
  • larger ecosystems can support longer food chains
38
Q

Why is only 60% of light that falls on leaves absorbed?

A
  • light could be the wrong wavelength
  • light can be reflected
  • light can be transmitted through the leaf
39
Q

What is photosynthetic ability and what is the equation for it?

A

A measure of ability of a plant to trap energy
PE = quantity of light energy incorporated in product / quantity of energy falling on plant x 100%

40
Q

What is gross primary productivity?

A

The rate of production of chemical energy in organic molecules by photosynthesis in a given area, in a given time
Measured in kJm-2y-1
(0.2-2%)

41
Q

What is net primary productivity?

A

Energy in the plants biomass which is available to primary consumers kJm-2y-1
(0.1-1%)

42
Q

What is the equation for net primary productivity?

A

NPP = GPP - respiration

43
Q

What is primary productivity?

A

The rate at which energy is converted by producers into biomass

44
Q

What is secondary productivity?

A

The rate at which consumers convert the chemical energy of their food into biomass

45
Q

Why is using pyramid of numbers a problem?

A
  • does not take into account the size of organisms
  • does not recognise the difference between juvenile and adult forms
  • range of numbers may be so large that it may be difficult to draw to scale
  • the pyramid may be inverted if one trophic level has more organisms than the previous one
46
Q

What is a pyramid of energy?

A

Most accurate way of representing feeding relationships, shows energy transferred from one tropic level to the next

47
Q

What are the problems with pyramids of biomass?

A
  • difficult to measure accurately
  • they do not indicate productivity or the amount of energy flowing through the system
  • may be inverted
  • some biomass is not transferred to the next trophic level
48
Q

What is meant by the term succession?

A

The change in structure and species composition of a community over time

49
Q

What is meant by the term climax community?

A

A stable, self perpetuating community that has reached equlibrium with its environment and no further change occurs

50
Q

What is meant by the term primary succession?

A

The change in structure and species composition of a community over time in an area that has not previously been colonised

51
Q

What is a pioneer species?

A

The first species to colonise a new area in ecological succession

52
Q

What is a sere?

A

The sequence of communities with different species and structures
Sere in a dry environment is a xerosere
Stages are called seral stages

53
Q

What are the seral stages for bare rock eroded by receeded ice to form a decidous forest?

A
  • first species to colonise the rock is algae (pioneer)
  • weathering and decomposition leads to primitive soil
  • wind blown spores allow mosses and other plants to grow
  • tall grasses allow shade tolerant species to become established
  • plants and animals die and decay, causing mineral rich soils
  • soil continues to deepen, broad trees can compete and establish
  • this forms a stable, self perpetuating climax community
54
Q

What is a climatic climax community?

A

The species of a climax community that largely depends on the climate

55
Q

When a climax community is balanced, what is there equilibrium between?

A
  • GPP and total respiration
  • energy used from sunlight and what is used in composition
  • uptake of nutrients for the soil and their return by decayed plant and animal remains
  • new growth and decomposition, so the quanity of humus is constant
56
Q

As a xerosere progresses, what are there increases in?

A
  • soil thickness and availability of water, humus and minerals
  • biomass
  • biodiversity
  • resistance to invasion of new species
  • stability to disruption by environmental challenges
57
Q

What is meant by secondary succession?

A

Recolonisation of a habitat previously occupied by a community but disturbed, for example by a tree falling or a fire

58
Q

What is meant by disclimax?

A

Human interference can affect succession and may prevent the development of the climatic climax community
examples
- grazing by sheep and cattle maintains grassland
- farming of land removes all introduced species

59
Q

What are the 4 phases of plant growth?

A

Pioneer - Building - Mature - Degenerate

60
Q

What are the 3 factors affecting succession?

A
  • immigration
  • competition
  • facilitation
61
Q

How does immigration effect succession?

A

The arrival of spores, seeds and animals is vital for succession to progress. Possibility of widely altering the community and the soil.

62
Q

What is the definition of intraspecific competition?

A

Competition between individuals of the same species, which is density dependent as the population increases, there is more competition.

63
Q

What is the definition of interspecific competition?

A

Competition between individuals of different species

64
Q

What is a niche?

A

The role and position a species has in its environment, including all interactions with the biotic and abiotic factors in its environment

65
Q

What is meant by facilitation?

A

The association between individuals of 2 species - symbiosis.

66
Q

What are the 2 different types of symbiosis?

A

Mutualism - an interaction between species which is beneficial to both (example flowering plants and pollinators like bees)
Commensalism - an interaction between species from which one benefits and the other is not affected (example a squirrel hiding from a predator in an oak tree)

67
Q

What are the 3 major proccesses in the carbon cycle?

A

Repiration
Photosynthesis
Decomposition

68
Q

What is the role of respiration in the carbon cycle?

A

Carbon dioxide is added to the air by respiration of animals, plants and microorganisms

69
Q

What is the role of photosynthesis in the carbon cycle?

A

Takes place on a large scale that it almost reuses all of the co2 as is released in the atmosphere

70
Q

What is the role of decomposition in the carbon cycle?

A

The dead remains of plants and animals are acted upon by detrivores and sapribionts in the soil, which ultimately release co2 back into the soil

71
Q

How does deforestation increase carbon dioxide content in the atmosphere?

A
  • the rate of which carbon dioxide is removed from the atmosphere by the process of photosynthesis is reduced by cutting down trees on a global scale, this is a massive reduction
  • when trees are cut down, they may be burned or left where they are cut to decay, both processes release co2 into the atmosphere
72
Q

What is the definition of global warming?

A

The increase of average global temperature, in excess of the greenhouse effect caused by the atmospheres historical concentration of carbon dioxide

73
Q

Explain the green house affect.

A
  • greenhouse gases include co2, methane, nitrous oxide, cfcs, ozone and water vapour
  • they allow high energy, short wavelength solar radiation to pass through to the earths surface, which warms up and re-radiates lower energy, longer wavelength infra-red radiation
  • this is absorbed and trapped by the greenhouse gasses in the atmosphere
  • the greenhouse effect is a natural process, without it the average temperature on earth would be about -20* and too low to sustain life
74
Q

What are some of the consequences to global warming?

A
  • polar icecaps are melting, flooding coastal areas
  • extreme weather conditions (droughts, hurricanes)
  • fires are more frequent and intense
  • ocean pH has decreased as more co2 dissolves
  • as ocean temperatures increase, a 1* rise is enough for corals to expel their mutualistic algae (bleaching)
  • water availability has decreased in tropical areas, epxanding desserts
  • evolutionary adaptation is slow so animals migrate
  • fishing areas and crop growing belts may move as climate changes
  • pests and pathogens may alter distribution, compromising health
  • crop yields may incraease to a certain extent, but in reas of extreme heat will die
75
Q

What is a carbon footprint?

A

The equivalent amount of carbon dioxide generated by an individual, a product or a service in a year.

76
Q

How do agricultural practices increase co2?

A
  • the production of farming tools
  • the production of insecticides, herbicides and fertilisers
  • farm machinery, powered by fossil fuels
  • transport of produce (air/sea miles)
77
Q

How can we use less co2 as a population?

A
  • recycle packing material
  • drive less
  • use less air conditioning and heating
  • reduce animal protein
  • avoid food waste
  • plant trees in deforested regions
78
Q

What are the 4 major processes in the nitrogen cycle?

A
  • ammonification
  • nitrification
  • denitrification
  • nitrogen fixation
79
Q

What is ammonification?

A
  • putting ammonium ions into the soil
  • detrivores consume dead organisms and decomposers secrete enzymes decaying remains
  • proteases digest proteins into amino acids
  • deaminases remove NH2 groups from amino acids and reduce them to ammonia ions NH4+
  • the digestion products are absorbed by the decomposers and are used by other organisms
80
Q

What is nitrification?

A
  • the addition of nitrogen to the soil, most commonly as nitrite (NO2-) and nitrate (NO3-) ions
  • ammonium (nitrosomonas) Nitrites (nitrobacter) Nitrates
  • processes lose hydrogen and gain oxygen, oxidation
  • the bacteria therefore require aerobic conditions
81
Q

What is denitrification?

A
  • the loss of nitrate from the soil
  • nitrate ions (pseudonomas) nitrogen
  • process loses oxygen so is reduction, the bacteria favours anaerobic conditions (like water logged soils)
82
Q

What is nitrogen fixation?

A
  • the reduction of nitrogen atoms in nitrogen molecules to ammonium ions, by prokaryotic organisms
  • azobacter is a free living nitrogen bacterium in soil
  • in legumes, rhizobium is found
  • nitrogen (red. nitrogenase ATP) ammonium ions (org acids, amino acids)
  • requires a reduction reaction (poisioned by oxidation) so leg-haemoglobin binds to oxygen in the nodules for protection (makes nods pink)
  • rhizobium doesnt occur naturally, both organisms produce chemo- attractants to find eachother
  • by death, both rhiz and legume decompose to form ammonia (mutualism)
83
Q

What non-biological processes have an impact on the nitrogen cycle?

A
  • application of fertilisers adds nitrogen to the soil
  • lighting adds a small amount of nitrogen to the soil
  • leaching of minerals removes nitrogen from the soil
84
Q

What human activities improve nitrogen in the soil?

A
  • ploughing fields improves soil areation
  • draining land
  • artificial nitrogen fixation (haber process)
  • large amounts of animal waste (manure)
  • treated sewage sludge, ‘biosolids’ sustainable alternative to fertilisers
  • planting fields of legumes enhances nitrogen fixation
85
Q

What is the definition of eutrophication?

A

The artificial enrichment of aquatic habitats by excess nutrients, often caused by run off fertilisers

86
Q

What are the 6 stages of eutrophication?

A
  • nitrate is a fertiliser and algae respond creating algal blooms, the water becomes green and light is unable to penetrate to any depth
  • the plants in deeper regions of the lake cannot photosynthesise and they die
  • there is a general decrease in animal species diversity as they rely on plants for food and shelter
  • the short lived algae soon die and decompose by saprobionic bacteria and fungi which are aerobic organisms, creating a biochemical oxygen demand (BOD)
  • the water in all but the upperlayers becomes deoxygenated so fish and other oxygen requiring species die
  • anaerobic bacteria in the water reduce nitrate to nitrite, they flourish and some release gases with a characteristic smell, such as hydrogen sulphide
87
Q

How can we reduce nitrogen in waterways?

A
  • restrict the amount of fertiliser applied to the soil
  • only apply fertiliser when plants are actively growing
  • leave a 10m strip wide from watercourses
  • dig drainage ditches
88
Q
A

A2 Biology (9 decks)

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