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Biology > Unit 4: Ecology > Flashcards

Unit 4: Ecology Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Population

A

Group of individuals of the same species living in the same area

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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
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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
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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)
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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

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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
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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)
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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

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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)

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10
Q

Life History

A

Traits that affect an organism’s schedule of reproduction and survival

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11
Q

Three main variables of life history

A
  1. Age of first reproduction
  2. How often organism reproduces
  3. How many offspring produced per reproductive episode
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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
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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

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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

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15
Q

r/k stragists + habitats

A

r strategists - habitats that are:
- Open/disturbed
- Temporary
- Unpredictable
K strategists - habitats that are:
- Permanent
- Crowded

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16
Q

Community

A

A group of populations of different species that live close enough to interact

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17
Q

Species interactions

A
  1. Competition
  2. Mutualism
  3. Commensalism
  4. Parasitism
  5. Predation
  6. Herbivory
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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)
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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
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20
Q

Ecological niche

A
  • The position of a species within the ecosystem
  • Its role in the ecosystem
  • Conditions necessary for its survival
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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
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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)
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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)

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24
Q

Symbiosis - mutualism

A
  • Help each other
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25
Q

Symbiosis - Commensalism

A
  • One organism helped by another, one is unaffected
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26
Q

Symbiosis - parasitism

A
  • One organism (parasite) gets nourishment for the other (host)
  • One benefits and the other gets harmed (rarely killed)
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27
Q

Endoparasites

A

Parasites live within the body of their host

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28
Q

Ectoparasites

A

Parasites feed on the external surface of a host

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29
Q

Pathogen transmission

A

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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30
Q

Brood parasitism

A
  • 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
31
Q

Predation

A

Predator kills and eats prey

32
Q

Evolutionary arms race

A
  • Predators have adaptations for eating
  • Prey have adaptations to escape/avoid being eaten
33
Q

Herbivory

A
  • 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
Q

Food webs

A
  • Made up of food chains
  • Food webs represent trophic interactions
  • (Vertical) position in the food web is called the ‘trophic level’
35
Q

Collared lemmings

A

Eat most plants, eaten by most predators

36
Q

Focal species

A

Some species that play a disproportionate role in the food web

37
Q

Types of species with a large impact

A

1) Dominant species (high biomass)
2) Ecosystem engineers (alter the physical environment)
3) Keystone species: despite low biomass and abundance, usually top predators

38
Q

Top-down control

A

Higher trophic level reduces the abundance or biomass of lower trophic level
- Ex. more herbivores, less plants / more carnivores, less herbivores, more plants

39
Q

Trophic cascade

A

Impact of top predators “cascades” down to lower trophic levels

40
Q

Sea Otter

A
  • Keystone species
  • Impact on community:
    1) fewer herbivores (sea urchins, starfish)
    2) More kelp
  • More productive
  • Physical structure
  • Fish species richness
41
Q

Regime shift

A

Abrupt shift to a very different and persistent community

42
Q

What causes regime shifts?

A

Usually external drivers:
- Removal of keystone species
- Arrival of disease
- Climate change
- Nutrient inputs

43
Q

Bottom-up control

A

Lower trophic level controls abundance or biomass of higher trophic level
- Ex. primary producers limit herbivore biomass

44
Q

Species richness

A

Number of species present in a community

45
Q

Disturbance

A

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)

46
Q

Why should we care about biodiversity?

A
  • 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
47
Q

Ecosystem

A

Organisms and abiotic environment

48
Q

Ecosystem Function

A
  • Species interactions (connections between components)
  • Energy and nutrient flows
49
Q

Connections in an ecosystem

A
  • Organisms to organisms
  • Organisms to the physical environment
50
Q

Energy flows

A
  • 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
Q

Nutrient flows

A
  • Circular flow of Nutrients: nutrients mostly retained. Cycle between organisms and physical environment
52
Q

Decomposers in nutrient cycling

A
  • Invertebrates, fungi, bacteria
  • Obtain chemical energy and nutrients from detritus (dead organisms)
  • Return some nutrients to physical environment
53
Q

Carbon Cycle

A

Plants get CO2 from atmosphere and convert to organic carbon (org C). Org C transferred among organism. CO2 returned to atmosphere through respiration.

54
Q

Carbon reservoirs

A

C is mostly stored in rocks and sediments. The rest is located in the ocean, atmosphere, and living organisms

55
Q

Range shifts

A
  • 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
Q

Coral bleaching

A
  • 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
Q

Ocean acidification

A
  • 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
Q

Nitrogen

A
  • Forms of organic nitrogen: DNA, RNA, proteins
  • Crucial for all living organisms
  • Required for photosynthesis
59
Q

Bacteria-driven nitrogen cycle

A
  1. N-fixation: N2 - NH4-
  2. Nitrification: NH4- - NO3-
  3. Denitrification: NO3- - N2
60
Q

Agriculture and N

A
  • Agriculture increases rates of N-fixation by
    1. Growing legumes
    (soybeans, peas, beans)
    2. Manufacturing fertilizer
61
Q

Legumes and N

A

Root nodules contain N-fixing bacteria (Rhizobium) (symbiosis - mutualism)

62
Q

Consequences of N fertilizer

A

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
Q

Coastal marine environments and N

A
  • 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
Q

Ecosystem health

A
  • 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
Q

Reasons to care about ecosystem health and function

A
  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
Q

Measures of ecosystem function

A
  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
Q

Net Primary Production (NPP)

A
  • Rate that plant biomass increases in an ecosystem
  • Biomass: Amount (mass) or organic matter present in an ecosystem
68
Q

Gross primary production (GPP)

A

Total light energy captured by plants

69
Q

Autotrophic respiration (Ra)

A

Energy lost due to plant respiration
NPP = GPP - Ra

70
Q

Net Ecosystem Production (NEP)

A
  • 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
Q

Positive NEP

A
  • Ecosystem biomass is increasing
  • Ecosystem absorbs more CO2 than it releases
  • Helps lower atmospheric CO2 (climate change)
72
Q
A
73
Q
A

Biology (5 decks)

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