Unit 4: Ecology Flashcards
1
Q
Population
A
Group of individuals of the same species living in the same area
2
Q
Measuring populations size: indirect indicators
A
- Less resources, less time, less costly
- Examples include
— # of nests, borrows, tracks
— Catch per unit effort (CPUE)
— Mark-recapture methods
3
Q
Mark-recapture methods
A
- capture + mark animals
- Take a second sample: based on how many marked are in new sample, can estimate pop. size
s = # marked and released in 1st sample
n = number of individuals in 2nd sample
x = total # of individuals already marked in second sample
estimate population size = N
Assumption: x/n = s/N
N = (s)(n) / x
4
Q
Mark-recapture assumptions
A
- Marked and unmarked individuals = same probability of being ‘captured’
- Marked individuals have mixed completely back into the population
- No individuals are born, die, immigrate, or emigrate during the sampling interval (short sampling interval)
5
Q
Exponential growth model
A
dN/dt = r N
dN/dt (delta pop. size/ delta time) = rate of change in a population
N: current population size
r: growth rate
larger r = faster growth
6
Q
Why does the population growth rate slow?
A
- Resources become limited
- Food and space
- This is because birth rates decline and/or death rates increase
- Density-dependent birth or death rates rugulate populations around an equilibrium
7
Q
What is carrying capacity?
A
- Carrying capacity (K) is the # of individuals of a pop. that an environment can support; birth rate (b) = death rate (d)
8
Q
Logistic growth model
A
dN/dt = rN (K-N/K)
- New term (K-N)/K reduces the rate at which the population grows as N increases
- If small N compared to K, r is larger
- If large N compared to K, r is smaller
- If N = K, the pop. stops growing
9
Q
Regulation processes
A
Bottom-up process: regulated by resources, they are the predators (top) eating food (bottom)
Top-down process: regulated by predation, prey (bottom) getting eaten (top)
10
Q
Life History
A
Traits that affect an organism’s schedule of reproduction and survival
11
Q
Three main variables of life history
A
- Age of first reproduction
- How often organism reproduces
- How many offspring produced per reproductive episode
12
Q
Reproduction trade-offs
A
- More offspring means less energy put into each one
- Alternatively, energy can be used to:
1. Increase offspring size
2. Provide parental care
therefore more likely to survive - Many offspring = each offspring low quality (many do not survive)
- Few offspring = Each offspring high quality, each likely to survive
13
Q
r vs. K strategists
A
1) r strategists: maximize # offspring
- Smaller offspring
- No parental care
2) Maximize offspring survival
- Larger offspring
- Parental care
14
Q
r/K strategists + environment
A
1) r strategy advantageous where quality matters little
- physically harsh environment:
- most offspring die anyway
- unpredictable environment:
- Most offspring will not survive
2) K-strategy advantageous where quality matter a lot
- Crowded or competitive environments:
- Stronger more likely to survive
- predictable environment
- Provisioning/caring increases survival
15
Q
r/k stragists + habitats
A
r strategists - habitats that are:
- Open/disturbed
- Temporary
- Unpredictable
K strategists - habitats that are:
- Permanent
- Crowded
16
Q
Community
A
A group of populations of different species that live close enough to interact
17
Q
Species interactions
A
- Competition
- Mutualism
- Commensalism
- Parasitism
- Predation
- Herbivory
18
Q
Competition
A
- Individuals of 2 species competing for resources required for growth and survival
- Both species do better without the other
- One will eventually outcompete the other (competitive exclusion)
19
Q
Interspecific competitors
A
- Use the same resource
- Resource is in limited supply
- Intertidal - space is the limited resource
Competition of resources:
—Lower birth rate (b)
—Higher death rate (d)
—Slower population growth (r) - Ex. Barnacles
20
Q
Ecological niche
A
- The position of a species within the ecosystem
- Its role in the ecosystem
- Conditions necessary for its survival
21
Q
Realized vs. fundamental niche
A
- Realized niche: the ‘observed’ niche that it occupies in the wild
- Fundamental niche: the conditions in which it can survive and reproduce
22
Q
Competitive exclusion principle
A
- If two species compete for one resource, the better competitor will eliminate the other
- Species must occupy somewhat different niches
(Two species cannot coexist in a community if their niches are identical)
23
Q
Character displacement
A
Evolution differences in morphology and resource use as a result of competition
- Can result in resource partitioning (one or more significant differences in their niches)
24
Q
Symbiosis - mutualism
A
- Help each other
25
Symbiosis - Commensalism
- One organism helped by another, one is unaffected
26
Symbiosis - parasitism
- One organism (parasite) gets nourishment for the other (host)
- One benefits and the other gets harmed (rarely killed)
27
Endoparasites
Parasites live within the body of their host
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Ectoparasites
Parasites feed on the external surface of a host
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Pathogen transmission
1) Direct: pathogens move from one host to the next
2) Indirect: pathogens use another organism (vector) to help them move (e.x. Lyme disease in ticks)
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Brood parasitism
- Brood parasitic birds lay their eggs in the nest of others
- Pass on the cost of rearing their offspring onto another individual (host)
- Can be intraspecific or interspecific
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Predation
Predator kills and eats prey
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Evolutionary arms race
- Predators have adaptations for eating
- Prey have adaptations to escape/avoid being eaten
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Herbivory
- Exploitative interaction (+/-) where an organism eats parts of a plant or algae
- Most herbivores are insects (e.g. grasshoppers and beetles)
- Can significantly influence their environment
34
Food webs
- Made up of food chains
- Food webs represent trophic interactions
- (Vertical) position in the food web is called the 'trophic level'
35
Collared lemmings
Eat most plants, eaten by most predators
36
Focal species
Some species that play a disproportionate role in the food web
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Types of species with a large impact
1) Dominant species (high biomass)
2) Ecosystem engineers (alter the physical environment)
3) Keystone species: despite low biomass and abundance, usually top predators
38
Top-down control
Higher trophic level reduces the abundance or biomass of lower trophic level
- Ex. more herbivores, less plants / more carnivores, less herbivores, more plants
39
Trophic cascade
Impact of top predators "cascades" down to lower trophic levels
40
Sea Otter
- Keystone species
- Impact on community:
1) fewer herbivores (sea urchins, starfish)
2) More kelp
- More productive
- Physical structure
- Fish species richness
41
Regime shift
Abrupt shift to a very different and persistent community
42
What causes regime shifts?
Usually external drivers:
- Removal of keystone species
- Arrival of disease
- Climate change
- Nutrient inputs
43
Bottom-up control
Lower trophic level controls abundance or biomass of higher trophic level
- Ex. primary producers limit herbivore biomass
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Species richness
Number of species present in a community
45
Disturbance
An event (ex. storm, overgrazing, human activity) that changes a community by removing organisms or altering resource availability (species richness may increase, decrease, or remain the same)
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Why should we care about biodiversity?
- Biodiversity is tied to ecosystem services, which are benefits people obtain from ecosystems
- Biodiverse ecosystems = more carbon sequestration
- Diverse habitats provide natural coastline protection
- Diverse habitats provide livelihoods (ex. fisheries)
- Diverse habitats provide a sense of place + well being
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Ecosystem
Organisms and abiotic environment
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Ecosystem Function
- Species interactions (connections between components)
- Energy and nutrient flows
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Connections in an ecosystem
- Organisms to organisms
- Organisms to the physical environment
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Energy flows
- Ecosystems (and life) are powered by the sun
- Primary producers capture radiant energy and store chemical energy (in molecular bonds in organic compounds)
- Ecosystems transfer chemical energy through consumption (transfer to consumers) and death (transfer to detritus)
- Ecosystems lose heat energy through respiration
- Energy transfer between trophic levels is typically only 10% efficient
51
Nutrient flows
- Circular flow of Nutrients: nutrients mostly retained. Cycle between organisms and physical environment
52
Decomposers in nutrient cycling
- Invertebrates, fungi, bacteria
- Obtain chemical energy and nutrients from detritus (dead organisms)
- Return some nutrients to physical environment
53
Carbon Cycle
Plants get CO2 from atmosphere and convert to organic carbon (org C). Org C transferred among organism. CO2 returned to atmosphere through respiration.
54
Carbon reservoirs
C is mostly stored in rocks and sediments. The rest is located in the ocean, atmosphere, and living organisms
55
Range shifts
- Climate change
- Species redistribute to stay within climatic niche
Generally leads to movement away from equator and towards poles
- On avg., 17 km/decade (terrestrial), 72 km/decade (marine)
- Also deeper (marine) / higher (terrestrial)
56
Coral bleaching
- Warming water causes corals to lose their symbiotic algae
- Repeated bleaching can permanently alter coral community
- Among the greatest threats to coral reefs today
- Unclear whether corals can adapt fast enough
57
Ocean acidification
- Input of carbon dioxide reduces pH (more H+) and carbonate ion concentration:
- Calcifying organisms (e.g. corals) have trouble building and maintaining calcium carbonate skeletons
58
Nitrogen
- Forms of organic nitrogen: DNA, RNA, proteins
- Crucial for all living organisms
- Required for photosynthesis
59
Bacteria-driven nitrogen cycle
1. N-fixation: N2 - NH4-
2. Nitrification: NH4- - NO3-
3. Denitrification: NO3- - N2
60
Agriculture and N
- Agriculture increases rates of N-fixation by
1. Growing legumes
(soybeans, peas, beans)
2. Manufacturing fertilizer
61
Legumes and N
Root nodules contain N-fixing bacteria (Rhizobium) (symbiosis - mutualism)
62
Consequences of N fertilizer
Long term impacts of excessive nitrogen inputs:
- High nitrate (NO3-) levels in soil water - can be toxic
- Pollution of aquatic ecosystems
(Unused nitrogen enters streams and rivers)
63
Coastal marine environments and N
- Eutrophication: Excessive primary production (algae) due to overload of nutrients
- Decomposition of algae leads to oxygen (O2) depletion
- Dead zone: low O2, fish and others die
64
Ecosystem health
- An ecosystem processes and transfers energy and nutrients
- Fueled by energy from outside the ecosystem
- Cycle and recycle nutrients from and to the physical environment
- An ecosystem might be 'unhealthy' if it is less able to:
- Obtain or transfer energy
- Cycle or retain nutrients
65
Reasons to care about ecosystem health and function
1. Feeding ourselves
- primary production: how fast can we grow food?
- Secondary production: how efficiently can we feed livestock animals?
2. Natural ecosystems
- Primary production: plants/tree abundance and recovery after damage
- Secondary production: Animal diversity and abundance
- Decomposition - nutrient supply
3. We are changing the rates
- Deforestation
- Use of fertilizers
- Greenhouse gas emissions and climate change
66
Measures of ecosystem function
1. Rate of primary production
- rate that primary producer biomass is built
2. Rate of secondary production
- rate that consumer biomass is built
3. Rate of decomposition
- rate that inorganic nutrients are released from detritus
67
Net Primary Production (NPP)
- Rate that plant biomass increases in an ecosystem
- Biomass: Amount (mass) or organic matter present in an ecosystem
68
Gross primary production (GPP)
Total light energy captured by plants
69
Autotrophic respiration (Ra)
Energy lost due to plant respiration
NPP = GPP - Ra
70
Net Ecosystem Production (NEP)
- Energy (biomass) accumulated in all ecosystem components (per unit time)
- Plants capture energy
- Energy stored as biomass in all organisms
- Heat energy lost from all organisms
NEP = GPP - RT
71
Positive NEP
- Ecosystem biomass is increasing
- Ecosystem absorbs more CO2 than it releases
- Helps lower atmospheric CO2 (climate change)
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