1
Q
Define population
A
All of the individuals of a species that live and reproduce in a particular place
2
Q
Population size
A
Number or individuals alive at a particular time in a particular place. Influenced by births, deaths and migration.
3
Q
N
A
Population size. Always rounded to nearest whole number
4
Q
B
A
Number of individuals born
5
Q
D
A
Number of individuals who died
6
Q
t
A
Time/generation
7
Q
b
A
Per capita birth rate
8
Q
d
A
Per capita death rate
9
Q
r
A
Per capita growth rate. r = b - d
10
Q
r > 0
A
Population is growing
11
Q
r < 0
A
Population is shrinking
12
Q
Population size at t+1
A
N_t+1 = (1+r)N_t
13
Q
N_t
A
N_t = N_o (1+r)^t
14
Q
Exponential model of population growth
A
r max. Predicts growth under ideal conditions but does not exist in reality.
15
Q
r max
A
Maximum intrinsic rate of increase. Always constant and positive. Varies by species and scales hypometrically with body size
16
Q
Bacteria r max
A
~10
17
Q
Human r max
A
~0.0001
18
Q
Larger organisms r max
A
Lower. Slower intrinsic rate of growth.
19
Q
Smaller organisms r max
A
Higher. Faster intrinsic rate of growth
20
Q
What limits population growth?
A
Factors that impact birth and death rates. Food, sunlight, predators, disease, shelter, water, mating partners, etc.
21
Q
As abundance increases, r will…
A
Decrease
22
Q
K
A
Carrying capacity. Point where births and deaths are equal and r=0
23
Q
Logistic model of population growth
A
Predicts population growth based on changing growth rates as populations reach carrying capacity (K). Assumes r decreases as population size increases.
24
Q
As N increases, r will…
A
Decrease
25
As r increases, N will…
Decrease
26
Rate at a given time (logistic model)
r_t = rmax ((K-N_t) / K)
27
Size of population (logistic model)
N_t+1 = N_t (1+r_t)
28
Heterotrophs
Organisms that cannot make their own food. Obtain energy by eating other organisms (plants, animals or both). Dependant on autotrophs
29
Secondary production
As animals eat plants, energy is transferred from producers to consumers. Some of the energy is stored in new consumer biomass
30
How do we know who is eating who?
Observation, stomach content analysis, scat analysis, stable isotopes (C, N, etc), or a combination of these
31
Energy and trophic levels
Producer - primary consumer - secondary consumer - tertiary consumer - quaternary consumer
32
Inefficiency of energy transfer between trophic levels…
Effects ecosystem structure
33
How much energy does each trophic level have compared to the one before?
About 10% on average
34
Decomposer food chains
Gain nutrients and energy from deceased animals
35
Reduced energy and biomass with increasing trophic levels effects…
Sizes of populations or organisms and the top of the food web
36
Tropic levels in nature
Many organisms consume different producers and consumers. Trophic levels may not be whole numbers (average of food sources)
37
Consumer biomass
Some energy stored in tissues
38
Ingestion
Energy consumed
39
Egestion
Energy excreted
40
Assimilation
Energy kept. Ingestion - Egestion
41
Net production efficiency (NPE)
How much energy is stored relative to energy assimilated from food. =Secondary productivity/assimilation
42
Secondary productivity (SP)
How much energy is stored. =assimilation - respiration
43
Net primary production (NPP)
Energy entering system. Determined by primary producer
44
Ecological efficiency (EE)
How much energy is in consumer biomass relative to net primary production. =Secondary productivity/NPP
45
Do real populations show logistic growth?
Sometimes yes, sometimes no
46
Do humans show logistic growth?
It is particularly hard to tell
47
Density dependence
Per individual rates of birth and death change as population density changes. Usually declines with increasing density. All populations experience it.
48
Why does density dependence occur?
Many reasons, usually biotic. Examples: predation, disease, competition for limited food, shelter, access to mates, etc
49
Effect of crowding on reproduction
Both plants and animals experience reduced reproductive success at higher densities
50
Effect of crowding on growth rate
Grow slower at high density and lower mass
51
Effect of crowding of adult size
Reduced adult size when planted at high density
52
Effect of crowding on survival
Organisms die faster when raised in high density
53
Crowding
Increased/high population density
54
Density independence
Factors that influence population growth and usually abiotic and related to the environment. Examples: temperature, precipitation, ocean acidity, disturbance (fire, flood, etc)
55
How could life history drive population genetics?
High rmax = high potential to overshoot K = unstable dynamics. Many poorly provisioned offspring = high mortality under bad environmental conditions.
56
How could population dynamics drive life history?
Natural selection may favour different traits and life histories at different densities (r vs K selection). Density near K may select for low fecundity/higher parental investment. Fluctuating densities might select for high fecundity/low parental investment/early maturation.
57
Ecosystem
A community of living organisms interacting with each other and their physical environment. Studied by following movement of energy from one level to the next
58
Abiotic
Non living. Ex. elements, climate, sunlight, air
59
Biotic
Living. Ex. microbes, plants, animals
60
Law of conservation of energy
Energy can be transformed or transferred but not created or destroyed
61
Law of entropy
Entropy of a system and surroundings will always increase. Energy always becomes more spread out
62
Law of conservation of matter
Matter can neither be created nor destroyed, only transformed. Matter is conserved and reused ex. C, N, P are recycled through ecosystems
63
Radiant energy
Energy from the sun. The source of nearly all energy on earth. About 33% is reflected back into space, 42% heats earths surface and >1% is captured by photosynthesizers to form base of ecosystems
64
Autotrophs
Producers. Synthesize organic compounds
65
Photoautotrophs
Use light energy to drive conversion of carbon dioxide into organic compounds. More prevalent because light energy is more abundant
66
Chemoautotrophs
Use chemical energy to drive conversion of carbon dioxide to organic compounds
67
Gross primary productivity (GPP)
The rate at which producers convert solar energy into chemical energy. Measured in kJ/m^2/time or C/m^2/time.
68
Net primary productivity (NPP)
The remaining chemical energy after deducting energy used for maintenance functions of producers. Measured in kJ/m^2/time or C/m^2/time.
69
Primary productivity in marine environments
Coastal zones due to nutrient runoff and sunlight. Areas with upwellings due to increased nutrients from deep ocean at the surface
70
Primary productivity limitations
Sunlight, climate, nutrients, how much photosynthetic tissue is present
71
Limiting nutrient
One nutrient usually has the greatest effect of capping productivity. Varies among ecosystems ex. Freshwater limited by P, terrestrial limited by N
72
Contaminant bio magnification
Lipophilic, synthetic compounds that bioaccumulate (increase in concentration over the life span of an organism) and biomagnify (increase in concentration with increasing trophic level)
73
Bottom up control
Abundance of organisms at lower trophic levels determines the abundance of organisms at higher trophic levels
74
Top down control
Predators at the top of the food web influence both the herbivores they eat and the plants on which the herbivores feed
75
Why is nitrogen often limiting?
N2 is abundant but not a useable form for plants. It has a triple bond that is hard to break.
76
Harber-Bosch Process
Harber produced a method to make ammonia from N2 and H gas and Bosch was an engineer who helped scale it up. Now accounts for half of all reactive nitrogen on Earth (affects ecosystems and contributes to eutrophication)
77
Greenhouse gas causal chain
Increased emissions - increased atmospheric concentrations - increased global surface temperature
78
Greenhouse gases
Ex CO2 from fossil fuel combustion, industrial processes, land use, forestry, CH4, N2O, fluorinated gases
Biol 213
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