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Ecology > UNIT 2: Community Structure and Biodiversity > Flashcards

UNIT 2: Community Structure and Biodiversity Flashcards

1
Q

Define “community”.

A

All populations inhabiting a given habitat.

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2
Q

What are the main trophic levels (food levels)?

A
  • Primary producers: plants, algae
  • Consumers: herbi-carni-omnivores
  • Decomposers: insects, invertebrates
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3
Q

What is the structure (species composition) of a community based on?

A
  • Climate
  • Available resources
  • Adaptive traits
  • Species interactions
  • Various population sizes
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4
Q

What is a niche?

A

A species’ occupancy in a community based on its tolerances and requirements (where and how species live). It describes how biotic and abiotic resources are used to ensure survival and reproduction.

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5
Q

What are the 2 types of niche?

A
  1. Fundamental: theoretical, life a species might have without interaction with others species
  2. Realized: actual, restricted life, relating to the presence of other species.
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6
Q

Describe interactions and what are the main types?

A

Define a species realized niche; can affect population sizes.

  1. Mutualism (+/+)
  2. Competition (-/-)
  3. Predation (+/-)
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7
Q

What is mutualism?

A

Mutualistic relationship is one in which organisms of DIFFERENT species interact to their mutual benefit.

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8
Q

Give an example of mutualism.

A
  1. The evolution of fruits and animals.
    - animals eat the plants and get the nutrients
    - plants seeds get dispered and gain reproduction.
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9
Q

What is the capture-recapture basic equation? Define all the variables.

A 
M/N = R/T
M: Total marked
N: Total population
R: Number recaptured
T: Total capture on 2nd visit
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10
Q

A group of students want to estimate the # of fish that live in a pond. They catch 45 and tag them. They return the 45 fish to the pond. The next day, they cath 60 fish, and 18 of them are tagged. Estimate how many fish live in the pond.

A 
M= 45
R= 18
T= 60
N= MT/R
N= (45*60)/18 = 150
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11
Q

What is the capture-recapture equation for repeated captures?

A

N= (M2C2 + M3C3)/R2+R3

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12
Q

If you were to mark a population of 23, and release them. then you caught another sample of 32, 4 of which were marked. The you caught a third sample of 28, 8 of which were marked, estimate the total poulation.

A 
M2=23
C2=32
M3= 23 marked at 1st + 28 newly marked = 51
C3=28
R2=4
R3=8

N= 180

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13
Q

What are the 2 types of competition?

A
  1. Intraspecific

2. Interspecific

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14
Q

Can competing species coexist?

A 
Sometimes, if enough resources.
In reality, the competitive abilities are rarely equal, so the POOR competitor 
-↓ in # 
-is relegated to poorer habitat
-goes extinct (long term)
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15
Q

Describe the Competitive Exclusion Principle.

A

No 2 species can coexist indefinitely on the same limited resources if they use it in the same way.

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16
Q

What is Resource Partitioning?

A

Also called a niche shift, it is a way to avoid or lessen competition by using a limited resource another way.

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17
Q

Give examples of resource partitioning.

A
  1. Live in same geographic area, but in different habitats
  2. Exploit the same habitat, but differently
  3. Exploit the same habitat, but at different times
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18
Q

Can a realized niche be bigger than a fundamental niche?

A

No. It can never happen because the fundamental niche is the theoretical niche when the species is alone (so the max), and realized is equal or smaller because of interactions and limitations.

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19
Q

What are the effects of predation on prey abundance?

A

Predators can regulate/control prey population size only if they kill more preys as prey pop ↑.

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20
Q

How can predators eat more prey? Is it increased if there is a preferred prey?

A
  1. # of predators ↑ (births, immigration)
  2. Predators focus on 1 type of prey (preferred prey)
  3. Each predator eat more prey (↑ availability of preys = ↑ opportunity to eat)

Yes it is increased if preferred prey.

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21
Q

More often, is it the prey pop that regulated the predator pop or the other way around?

A

The prey pop that regulated the predator pop

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22
Q

Predator or Prey:

Which reproduces quicker?

A

Prey.

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23
Q

Describe the “coevolutionary Arms Race”

A
  1. Preys become more efficient at escaping predators
  2. Predators become more efficient at catching preys
  3. Step 1 again
  4. Step 2 again
    never ending cycle
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24
Q

Why don’t preys or predators become so good that it causes the other to go extinct?

A
  1. Most predators eat more than 1 prey
  2. Life-dinner principle: more pressure on the prey to escape
  3. Preys are usually 1 step ahead in the arms race bc of short reproductive time
25
Q

Do all prey/predator populations cycle drastically?

A

NO. Stable pop of both prey and predator are possible if predators keeps prey pop from overshooting K.

26
Q

How can predation improve vitality of prey pop?

A
  • Surviving preys have less intraspecific comp = ↑ resources
  • Weaker preys get eaten = stronger prey pop left
  • Predation helps to ↑ biodiversity (removing dominant species favors biodiversity because other species can grow)
27
Q

Name adaptations of preys to escape predators.

A
  • Camouflage
  • Warning coloration
  • Mimicry
28
Q

Name and describe the 2 types of mimicry.

A
  1. Batesiam: one edible sp (mimic) will imitate the toxic sp (model)
  2. Mullerian: 2 or more poisonous sp looking th same reinforce lessons learned by a predator that attacks any sp in the mimicry complex (all models)
29
Q

Which type of mimicry is most efficient between Batesiam and Mullerian and why?

A

Mullerian is most efficient, because there are more spp that teach the behaviour, whereas in the other type sometimes the predator can eat the edible prey so the behaviour is not taught. So the % of mimics matter, the more, the less efficient it is.

30
Q

What is predation between individuals of the same sp called?

A

Cannibalism (+/-)

31
Q

What promotes cannibalism?

A
  • pop strees (starvation, crowding)

- presence of vulnerable individuals (eggs, juveniles, old, sick)

32
Q

How can cannibalism be advantageous?

A
  • May be a mechanism for pop control/regulation

- Eating offspring if doomed to die = ↑ parent’s survival = ↑ parent’s other offsprings’ survival

33
Q

What is parasitism?

A

(+/-) Organism (parasite) living in/on another organism (host), usually not killing it because it is physically dependent on the host.

34
Q

What are the 2 types of parasitism?

A
  1. True parasitism: physical association; may affect pop size of host
  2. Social parasitism: social association; intraspecific; laying eggs in other female’s nest, queen bee killing another queen
35
Q

What is commensalism?

A

Relationship between 2 spp where one gains/takes something from the other without harming it.

36
Q

Give an example of commensalism.

A

Bromeliad plant on tree: gets all nutrients from aerial roots, gets support without affecting the tree

37
Q

Define community stability.

A

The ability of a community to rebound from a disturbance

38
Q

What are the 3 types of model that contribute to the community stability?

A
  1. Successional
  2. Climax Pattern
  3. Cyclic Changes
39
Q

Describe the Successional model.

A
  • Climate based
  • Progressive replacement of 1 community by another
  • Often progresses to a STABLE ENDPOINT (stable terminal community, which we call the climax community (self perpetuating)
  • Primary and secondary succession
40
Q

Describe the primary succession of the Successional model.

A

When the 1st vegetation starts to grow
When vegetation and/or soil are absent (previously destroyed)
-take a lot of time (1000 years)

ex: Glacier retreat, volcanic eruption

41
Q

What are the steps of the primary succession of the Successional model.

A
  1. Formation of soil by weathering
  2. Lichens (do not grow fast)
  3. Mosses→Insects→Grass→Animals→Bushes→Trees
  4. = Climax community (mature community)

Organisms progressively get replaced.

42
Q

Describe the secondary succession of the Successional model.

A

Occurs in areas not totally stripped of vegetation/soil

  • takes 100-200 years
    ex: fire occurs but some vegetation remains
    ex: lake succesion
43
Q

Why does lake succession occur?

A

Plants need sunlight, water and nutrients to grow

  • pioneer sp take advantage of high light levels and low nutrients, but they are soon shaded by newcomers
  • pioneer sp tend to make the env less favorable for themselves and more favorables to others because they produce nutrients that others use to grow bigger and taller = interspecific competition
44
Q

Describe the Climax-Pattern model.

A

A model that states that factors other than climate affect the climax community such as: type of soil, wild fires, wind, chance, T, spp interactions, moisture,…

45
Q

Describe the Cyclic Changes model.

A

This model states that to remain stable, certain communities require episodes of instability to maintain climax spp (climax communities)

Examples of beneficial periods of instability:

  1. Wild fires in forests
  2. Periodic drought in prairies allowing new plants to grow
46
Q

Some factors may permanently change a community and will bring it to a terminal endpoint (new climax community). What is the types of species that can do this?

A

Keystones species and Exotic species.

47
Q

Describe the concept of keystone species.

A
  • The sp is essential to the stability of the community
  • Its influence in a community is DISPROPORTIONAL to its numbers → small in number but holds the whole community together
48
Q

Give an example of a keystone sp and explain why it is considered a keystone sp.

A

Sea otters in ocean who are not very numerous and feed on sea urchin, which are very large in number. Sea urchin cuts kelp algae “foot” so the algae stops growing. The community has no more kelp algae and has a lot of sea urchin when there are no otters.

In presence of sea otters, kelp algae can grow because sea urchin are controlled and eaten by sea otters. Their effect is much larger than their #

-effect is disproportional to the size of the sp.

49
Q

Explain the concept of dominant sp and how it is different from Keystone sp.

A

The dominant sp is the most abundant in # or in biomass in a community, whereas the keystone sp is usually fewer in # than other spp in the community. There are usually 1 or 2 dominant spp per trophic level.

50
Q

How do you achieve abundance? (dominant sp)

A
  1. Good competitors
    -generalist sp that feeds on everything
    -specialist sp that feeds on 1 widespread common
    resource
  2. Colonize new habitats & ↑ # quickly
51
Q

What problematics do exotic species (non-native spp) cause?

A
  1. May be competition/predation to native species
  2. May have no predator
  3. May be pathogenic
52
Q

What are the 3 ways to evaluate species biodiversity?

A

1) Species richness: # of different spp
2) Shannon’s diversity index: abundance of different spp
3) Shannon’s eveness index: distribution of different spp

53
Q

What is the importance of biodiversity?

A
  • Ecological services to maintain ecosystem stability: providing foos, O2, CO2, nutrients recycling, controlling erosion..
  • Intrinsic value: value regardless of benefits
  • Belief in its important
  • Utilitarianism: the usefulness and useful properties of plants
54
Q

In general, where are most species found on Planet Earth? why?

A

In the tropics & subtropics (around the equator)

  • warmer T
  • more rainfall
  • more ligth
  • longer growing season
  • reliable/stable conditions
55
Q

What is the effect of reliable resources around the equator for spp?

A

Reliable resources → more individuals → more competition → resource partitioning/niche shift → specialization → more # of spp

56
Q

What is the effect of Islands on species richness?

A
  • Distance from mainland, if ↑, biodiversity ↓.

- Island area, if ↑, biodiversity ↑.

57
Q

Describe the effect of island size on extinction and immigration rate.

A

Extinction rate:

  • small island = ↑ extinction rate
  • large island = ↓ extinction rate

Immigration rate:

  • small island = ↓ immigration rate
  • large island = ↑ immigration rate
58
Q

Describe the effect of distance from mainland of an island on extinction and immigration rate.

A

Extinction rate:
always the same

Immigration rate:

  • far island = ↓ immigration rate
  • near island = ↑ immigration rate

Ecology (5 decks)

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