Populations And Ecosystems🌍 Flashcards
(110 cards)
1
Q
What is a fugitive species?
A
- Large capacity for reproduction and dispersal
- Pioneer species
- Opportunistic - avoids competition
- Continually invade new environments to survive
- Boom-bust population growth
2
Q
What is an equilibrium species?
A
- Competition in habitat controls population size and drives adaptations
- Fewer offspring - survive longer
- Sigmoid growth curve
- Populations stabilises
3
Q
What is a pioneer species?
A
- The first to colonise previously biodiverse ecosystems
* Able to withstand harsh conditions
4
Q
Examples of density independent factors
A
- Favourable light (increase pop)
- Plentiful space (increase pop)
- Sudden change of abiotic conditions (decrease pop)
- Too little light (decrease pop)
- Limited space (decrease pop)
5
Q
Example of density dependent factors
A
- Less parasitism (increase pop)
- Inadequate food supply (decrease pop)
- Disease as pathogens (decrease pop)
- Increased predation (decrease pop)
6
Q
What is an ecosystem?
A
A community of organisms that interact with each other and the abiotic factors of their habitat
7
Q
What is a population?
A
A group of interbreeding individuals of the same species found in a particular habitat at a particular time
8
Q
What is a community?
A
Populations of different species living in a particular habitat at a particular time
9
Q
What is a habitat?
A
The physical environment where a particular population or community is found
10
Q
What is an environment?
A
The set of external conditions (biotic and abiotic) that surround an organism
11
Q
What is an ecological niche?
A
The role and position of a species in its environment, including all interactions/adaptations with the biotic and abiotic factors
12
Q
What is an invasive species?
A
- Species introduced to an area
* Can outcompete other species
13
Q
Can ecologically similar species coexist?
A
Yes, if they have slightly different niches
- there will be more of one species than the other
14
Q
What is the lag phase? (Phase 1)
A
•Slow increase to number in the population
- adjusting to new environment
- time needed to produce enzymes and switch on genes
- few reproducing individuals
15
Q
What is the exponential growth/log phase? (Phase 2)
A
•Population grows at biotic potential (max rate)
•No limiting factors
-plentiful nutrients
-low concentration of waste products
16
Q
What is environmental resistance? (Phase 3)
A
•Environmental factors slow population growth
•Limiting factors inhibit further growth
-low food
-overcrowding
-competition
-toxic waste accumulation
17
Q
What is the stationary phase? (Phase 4)
A
- Carrying capacity is reached
- Equilibrium is established
- Death rate = birth rate
18
Q
What is carrying capacity?
A
The maximum population size that an environment can support indefinitely
19
Q
Boom and bust curve
A
•Sometimes, a population increases so rapidly during the exponential growth phase that it overshoots the carrying capacity
•As environment cannot support population, a population crash usually follows
•Overpopulation can damage the environment
-new, lower carrying capacity
20
Q
Abiotic factors that increase/decrease a population size
A
- Space
- Water supply
- Light intensity
- Stability of abiotic factors
21
Q
Biotic factors that increase/decrease a population size
A
- Food supply
- Disease resistance
- Number of predators/ability to avoid
- Reproductive rate
22
Q
What are density dependent factors?
A
•As a population density increases, these factors have stronger effects
-affecting a larger proportion of the population
•Involves intraspecific competition
•Usually biotic factors
23
Q
What are density independent factors?
A
- Affect the same proportion of the population, no matter what density
- Usually abiotic factors
24
Q
How can abiotic factors indirectly affect organisms?
A
By affecting their food source
25
What is immigration?
Amount of movement into a population
26
What is emigration?
Amount of movement out of a population
27
What is competition?
When two or more individuals have to share resources in short supply
-one may be outcompeted
28
What is interspecific competition?
Competition between members of two different species
| -predator-prey
29
What is intraspecific competition?
```
Competition between members of the same species
E.g.
-mate selection
-food sources
-territory
-nest sites
```
30
What is the competitive exclusion principle?
* When the ecological niches of two species are so similar that they compete for the same similar resources
* They cannot coexist together indefinitely
31
What is a realised niche?
Restricted by the presence of a competitor
32
What is a fundamental niche?
The larger, potential niche that would occur without the competitor
33
What is resource partitioning?
The division of environmental resources between two organisms/species
34
What is ecological succession?
The gradual change from one community type to another (structure and species composition)
35
What is primary succession?
* Occurs in any newly formed area where no life previously existed
* Is a slow process
36
What is secondary succession?
* Occurs in areas where life is already present but has been altered in some way
* The species recolonise the area
* Faster process
37
Why is secondary succession faster?
* The soil is already deep and rich in nutrients
* There may be seeds/bulbs already in the soil
* Pioneer stages are not needed
38
Explain the process of succession?
•Pioneer species colonise the area
-adapted to survive and reproduce in harsh conditions
•Pioneer species stabilise the substrate and alter the abiotic conditions
-erode rock, add nutrients/inorganic matter and upon death add organic matter to the soil
•Due to change in abiotic conditions, new species have advantages that allow them to outcompete the pioneer species (C.E principle)
•Process continues - as one community alters the abiotic environment, new species will migrate and outcompete those species, allowing a new community to take over
•Succession progresses through various seral stages before reaching a climax community
39
What is a climax community?
* The final stage of succession
* Stable
* Long-living plants
* Complex food webs
* High biodiversity
40
What are seral stages?
The different stages in succession when particular communities dominate
41
How do the organisms differ from one stage to another?
Types of animals and plants will differ from one seral stage to another
42
How does succession affect biomass?
* An increase in biomass occurs with succession
* As soil becomes deeper and more rich with organic debris and nutrients, it an support a larger number of plants and animals
43
How does succession affect biodiversity?
An increase in plant and animal diversity
44
Why does a diverse plant community increase animal diversity?
* It provides more resources/food/habitat
| * It provides more ecological niches
45
What is climatic climax?
When a climax community is reached, it is in equilibrium with the climatic conditions
46
Interference with a climatic climax
•Humans and other animals can interfere
-a different equilibrium, known as the biotic climax may be reached
•Management of land by intensive grazing, seasonal mowing, burning or weed spreading are all examples of this climax
-often referred to as a deflected climax
47
What is deflected climax?
Plant succession deviating from its normal course due to direct or indirect human intervention
48
What does succession lead to?
* Increase in number of available niches
* Increase in species diversity
* Increase stability of ecosystem
49
What’s a random sample?
* Random numbers are generated to produce coordinates
* A tape measure is used to create a sample area
* A sample is taken at the coordinates
50
What’s a systematic sample?
Sampling points are taken at regular intervals
51
Why are transects useful?
Record changes in abundance and distribution of a species where a transition occurs
52
What is a line transect?
Tape is put across the sample area and any species that touch it are recorded
53
What is a belt transect?
Transect is put along tape at intervals and the species found within it are estimated
54
What is a frame quadrat?
* Laid down at sampling points within a sample area or at points along a transect
* Organisms are estimated (often as % cover)
55
What is a point quadrat?
* 10 pins dropped through frame onto vegetation
| * As each pin touches a plant of a particular species, a hit is recorded
56
What is a problem with random sampling?
It may miss areas, so some species may be missed
| -biodiversity is underestimated
57
What are the different measures of abundance?
•Density
-mean number of individuals per unit area
•Frequency
-number/percentage of sampling units in which a particular species occurs
•Biomass (standing crop)
-dry weight of plants or animals in a certain area at a certain time
•Percentage cover
-% of ground covered by a species within the sampling unit
58
Simpson’s diversity index
D=1-(En(n-1)/N(N-1))
•D=diversity
•n=total number of organisms of a particular species
•N=total number of organisms of all species
59
Why take a sample?
•Time and cost
•Provides estimate
•More samples=more reliable mean and anomalies have less effect
-sample is more representative
•Large sample size minimised possibility that the sample may be unrepresentative
•Random to avoid bias
60
What is a food chain?
* Shows a sequence of organisms in which each organism is the food of the next one in the chain
* Show direction of flow of energy
* Each organism represents a trophic level
61
What can food chains show?
How substances such as pesticides/insecticides are transferred in an ecosystem
62
Limitations of a food chain
* Do not reflect the complex feeding relationships that exist in most ecosystems
* Give false impression that each organism only feeds on one other type of organism
63
What is a food web?
Interconnected food chains
64
Limitations of a food web
•Relationships can be complex
-related species with similar diets are grouped together
•Only a part of the ecosystem is usually shown
•Doesn’t say how much energy flows from one part of an ecosystem to another
65
What is a pyramid of number?
* Shows quantitative relationships between organisms at each trophic level
* Represents the total number of organisms at each trophic level in a food chain at a given point in time
* May be inverted
66
What is a pyramid of biomass?
* Takes into account the difference in size between organisms
* Counts the number of individuals presents (in each trophic level) in a given area and multiplying it by the average mass of these individuals
* Can be inverted
67
What is biomass measured in?
kgm-2
68
Why don’t pyramids of biomass give a meaningful comparison between masses of the same trophic level in different ecosystems/different trophic level, same ecosystem?
* Usually refers to the standing crop
| * Biomass of populations of small organisms may fluctuate throughout the year
69
What is standing crop?
Amount of dry mass measured at any one time
| -have to dry out organism or use estimate
70
What is a pyramid of energy?
* Represent a flow of energy through each trophic level in an ecosystem during a fixed period of time (kJm-2y-1)
* Allow comparisons between the productivities of the trophic levels because a time period is involved
* Never inverted
71
How can energy flow be presented?
* Pyramid of energy
| * Energy flow diagram
72
Efficiency of primary production
* Proportion of solar energy converted into the chemical energy of plant tissues is low
* GPP
* NPP
73
What is gross primary production? (GPP)
The total rate autotrophs synthesise organic material
74
What is net primary production? (NPP)
The rate at which autotrophs store organic material as new plant tissue (available for primary consumers)
75
Equation for NPP
NPP = GPP - energy lost during respiration
76
Efficiency equation
```
Efficiency =
energy/biomass after transfer
/
energy or biomass before
x100
```
77
Why isn’t the majority of light converted?
•Some light is reflected off the plant surface
•Some light fails to strike a chlorophyll molecule
-transmitted through the leaf
•Some light is of the wrong wavelength for photosynthesis
78
What is secondary production?
•The rate at which energy from one trophic level is used to make new animal cells/tissue
•Approx 10% of energy passes between levels
-number of trophic levels is usually limited to 4/5 in an ecosystem
79
What factors contribute to a loss of energy in a food chain?
* Parts of the organism are not eaten
* Parts of the organism are not digested
* Energy is lost as heat to the surroundings during cellular respiration
80
How to use log scales for drawing population graphs
* log10(—) on the calculator
* Find for all values - put values onto a graph
* It tells you the number of times that 10 has been multiplied by itself to get a number
81
How to read off a log graph
* Press shift
* Press log
* Add number
82
What is nitrogen used for by plants?
* Produce amino acids
* Produce DNA
* Produce RNA
83
Alternative ways nitrogen fixation can occur
•A little can occur during thunderstorms
-lightning provides energy to oxidise nitrogen to nitrogen oxides
•Artificially by industry
-produces nitrogen fertilisers
84
What mostly carries out nitrogen fixation?
•Nitrogen fixing bacteria - nitrogenase
•Rhizobium
-mutualistic bacteria found in root nodules of leguminous plants
-plants obtain source of nitrogen, while bacterium gains a home and constant source of carbohydrates
•Aztobacter
-found living free in the soil
85
How does ammonification/putrefaction occur?
•Ammonia is produced from organic nitrogen-containing compounds
-found in faeces, urine and dead organisms
•Carried out by saprophytic bacteria and fungi
-decompose/metabolise compounds
-release ammonium ions
86
How does nitrification occur?
```
•Under aerobic conditions
•Nitrifying bacteria (chemoautrophs)
•Nitrosomonas convert:
-ammonia to nitrites
•Nitrobacter convert:
-nitrites to nitrates
```
87
How does denitrification occur?
* Denitrifying bacteria pseudomonas convert nitrates and ammonium ions into atmospheric nitrogen
* Occurs in anaerobic conditions (waterlogged soils)
* Removes nitrogen from ecosystems
88
What is assimilation?
When an organism absorbs small soluble products and use them to synthesise it’s own organic molecules
89
Equation of nitrogen fixation
Nitrogen + hydrogen
——>
Ammonia
90
```
Molecular formulae for:
•Atmospheric nitrogen
•Ammonium ion
•Nitrites
•Nitrates
```
* N2
* NH+4
* NO-2
* NO-3
91
What is the main source of carbon for terrestrial and aquatic organisms respectively?
•Terrestrial: carbon dioxide
•Aquatic: hydrogencarbonate ions formed from dissolved carbon dioxide
-as CO2 conc increases in atmosphere, more becomes dissolved in water
92
How is CO2 fixed?
* Photosynthesis by photoautotrophs - convert it to complex organic molecules
* CO2 is then returned to oceans and atmosphere by respiration
* Carbon is also released during decomposition
93
How is CO2 released into the atmosphere?
* Combustion of fossil fuels
| * Deforestation
94
Effects of global warming
* Altered rainfall patterns
* Desertification
* Rise in sea levels
* Floods
* Forest fires
95
Effects of climate change
* Affects distribution of species
* Can lead to extinction of species
* Can affect crop yields (can improve)
96
What is a carbon footprint?
Individual contribution to CO2 emissions over a year period
97
Effects of global warming on agriculture
* Increased frequency of weather extremes
* Loss of biodiversity
* Loss of fertile coastal lands caused by rising sea levels
* Dramatic changes in distribution and abundance of fish
* Increase in incidence of pests and vector-borne diseases
* More unpredictable farming conditions in tropical areas
98
What is biological oxygen demand (BOD)?
* Adding organic material to water stimulates the growth of microorganisms which feed on the material
* As the density of microorganisms increases, their demand for oxygen also rises
* mgdm3
99
What is leaching?
When nitrates and phosphates enter water
-by sewage
-by agricultural runoff
Leads to eutrophication
100
Process of eutrophication
•Nitrates enter water by leaching
•Causes algal blooms which:
-smother plants
-reduce light intensity (plants are unable to photosynthesise)
-produce toxins which kill organisms
•Algae and other organisms die and are decomposed by saprophytic bacteria
•Deoxygenation occurs due to bacteria multiplying
-causes more aerobic organisms to die
101
Why might a farmer plough their field?
* Adds oxygen to soil
* Provides aerobic conditions
* Aztobacter carry out nitrogen fixation
* Adds ammonium ions to the soil
102
Why might a farmer rotate crops with legumes?
* Leguminous plants contain Rhizobium in their root nodules which carry out nitrogen fixation
* Ammonium is added to the soil
103
Why might a farmer add manure to the soil?
* Manure is decomposed by saprophytes
* Ammonification occurs
* Ammonium is added to the soil
104
Why might a farmer have good drainage?
•Waterlogged soil provides anaerobic conditions
- prevents nitrogen fixation by Aztobacter
- encourages denitrification which adds N2 to the atmosphere
105
Equation for population growth
Population growth=
Births + immigration
-
Deaths + emigration
106
What type of competition causes succession?
Interspecific
| -plants competing for the same resources
107
What is the benefit of intensive farming?
•Animals are kept indoors in high densities under temperature controlled conditions
•Increases efficiency of meat production (secondary productivity)
-reduces respiratory losses due to movement and regulation of body temperature
108
Function of leghaemoglobin
* High affinity for oxygen - binds with lots of oxygen
* Lowers oxygen levels in the root nodules
* Can fix atmospheric nitrogen without oxygen
109
GPP = ?
Solar energy - energy not used
110
NPP = ?
GPP - respiration
