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biology > Lecture 31 - Ecology (part 2) > Flashcards

Lecture 31 - Ecology (part 2) Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What do populations have the potential to do?

A

to expand in size when resources are abundant and conditions are ideal

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2
Q

What is population size determined by in an IDEAL environment?

A

is determined by births, immigration, deaths, and emigration

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3
Q

If we ignore immigration/emigration, we can represent:

A

the change in population (N) over time (t) as the number of births (B) – deaths
(D)

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4
Q

What do ecologists like to use?

A

like to use models that describe per capita (per individual)

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5
Q

What does the per capita change in population size (rΔt) represent?

A

the contribution that an average member of the population makes to the number of individuals added/subtracted during a time interval
• Ie if a population of 1000 increases by 16 individuals per year, it has a
per capita change of 16/1000
• If we know the per capita change and the size of the population, we
can calculate R

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6
Q

How can you calculate the change at an instance of time?

A

using differential calculus

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7
Q

Change in Population =

A

Births + Immigrants – deaths – emigrants

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8
Q

Exponential growth

A

Populations whose members all have access to abundant food and resources grow rapidly

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9
Q

The resulting plot of exponential growth has a…

A

“J” shaped curve

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10
Q

“J” shaped curve

A
  • The per capita rate of increase remains constant (and equals r)
  • The number of individuals added to the population gets larger and larger per unit time
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11
Q

Example of exponential growth:

A

Population has a constant growth rate of 2 will increase by 40 individuals per unit time but will add 200 individuals when the population size is 100.

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12
Q

Populations with HIGHER rates of increase (r=1) will grow _____ than one with LOWER rates of increase (r=0.5)

A

faster

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13
Q

Exponential growth is a characteristic of…

A

populations that are introduced to new environments or in populations rebounding from a drastic event

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14
Q

Logistic growth

A

Environments have limited resources, and as populations increase, the resources decrease

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15
Q

Carrying capacity (K)

A

is the MAXimum population size that an environment can sustain
• If a population doesn’t have enough resources, birth rates decrease and the populations decline

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16
Q

Logistic growth models are…

A

sigmoidal (S-shaped), that is the population per capita growth approaches zero as K is reached

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17
Q

(K-N)

A

Number of additional individuals the environment can support

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18
Q

K

A

Carrying capacity

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19
Q

dN/dt=rN(K-N)/K

A

Fraction of K that is still available for population growth

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20
Q

When N less than K…

A

(K-N)/K is close to 1 and per capita growth rate is high (and close to r)

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21
Q

When N>K…

A

(K-N)/K is close to 0 and per capita growth rate is low

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22
Q

When N=K…

A

the population will stop growing

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23
Q

New individuals are added to the population most rapidly during what?

A

during the intermediate population sizes

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24
Q

Why are new individuals added to the population most rapidly during the intermediate population sizes?

A
  • Enough breeding individuals available

* Available space and resources still abundant

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25
Q

So WHY does the population growth rate decrease as N approaches K?

A
  • Birth rate DEcreases
  • Death rate INcreases
  • Both birth rate decreases and death rate increases
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26
Q

What are the assumptions that logistic models have that do not really fit real biological scenarios?

A

• Assumes populations can adjust instantaneously to increase density by lowering birth rates or raising death rates (there is often a delay)
- Populations will often overshoot carrying capacity temporarily

• Assumes environment doesn’t change

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27
Q

Community interactions are…

A

dynamic!

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28
Q

Biological community

A

is a group of populations of different species that live close enough to interact

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29
Q

Interspecific interactions

A

are interactions between different species

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30
Q

Types of Interspecific interactions:

A
  • Competition -/-
  • Predation +/-
  • Herbivory +/-
  • Parasitism +/-
  • Mutualism +/+
  • Commensalism +/0
  • Altruism (facilitation) +/+ or +/0
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31
Q

What do species interactions influence?

A

the community composition

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32
Q

Species decline or increase abundance as…

A

interactions alter survival or reproductive rates of others

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33
Q

Interactions can also influence what?

A

evolution of species, changing their morphology, physiology, and behavior

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34
Q

What do kelp forests provide?

A

food and shelter for a variety of species

35
Q

What can Sea urchins do?

A

decimate kelp forests, affecting the other members in the community

36
Q

Competition benefits…

A

no one!

37
Q

Interspecific competition

A

is a negative ecological interaction

- aka no one benefits

38
Q

What do individuals of different species compete for?

A

limiting resources (resources that are required for growth and development)

39
Q

Examples of Interspecific competition:

A
  • Garden weeds compete with planted flowers for soil nutrients and water
  • Grasshoppers and bison compete for grass to eat
40
Q

Competitive exclusion

A

occurs when one species uses the resources more efficiently than the other species

41
Q

What does competitive exclusion lead to?

A

Leads to one species being stronger and more fit (higher reproductive success) than the other species
• Eventually causes local elimination of the inferior competitor

42
Q

What did G.F. Gause study & what did he find?

A

studied Paramecium aurelia and P. caudatum

  • When grown in culture separately, grew logistically and reached carrying capacity
  • When grown together, P. caudatum became extinct in the culture since P. aurelia appeared to have a competitive edge
43
Q

Ecological niches determine…

A

resources!

44
Q

Ecological niche

A

An organism’s ecological niche contains all of the abiotic and biotic resources a species needs to survive

45
Q

What can an organism’s ecological niche include?

A

Can include

  • temperature
  • size of habitat structures (trees, branches, rocks, etc)
  • food availability
  • moisture
  • etc
46
Q

What happens if two species ecological niches are identical?

A

then the two species cannot coexist in the same community
• Resource partitioning allows species to coexist
• Species are able to use some, but not all of the shared niche

47
Q

What does resource partitioning allow?

A

allows species to coexist

• Species are able to use some, but not all of the shared niche

48
Q

Fundamental niches

A

are the niches potentially occupied by that species

49
Q

Realised niches

A

are the portion of the niches a species actually occupies

50
Q

Explain what Joseph Connell did…

A

removed a barnacle species residing beside another one to see if the reason for the stratification was due to interspecific competition
• It was! Chthamalus was able to colonise lower tidal zones when Balanus was removed

51
Q

What can ecological niches result in?

A

character displacement in order to reduce competition (ex Galapagos finches)

52
Q

Exploitation benefits…

A

only one species

53
Q

Any +/- interaction is a form of…

A

exploitation

54
Q

Predation

A

is a +- exploitive interaction where one species (predator) EATS another animal (prey)

55
Q

Animals that eat seeds are also considered…

A

predators

56
Q

Predators are _________ affected by humans

A

disproportionally

57
Q

How are predators disproportionally affected by humans?

A
  • We killed off wolves that ate our sheep (still cull wolves in BC)
  • These have huge affects on the community structure
  • Predator-prey relationships are very interconnected
  • Higher prey abundance leads to higher predator abundance and vice versa
58
Q

Predator-prey relationships are very…

A

interconnected

• Higher prey abundance leads to higher predator abundance and vice versa

59
Q

What have prey evolved?

A

behavioural, mechanical, and chemical adaptations to help reduce predation

60
Q

Examples of what prey have evolved behavioural, mechanical, and chemical
adaptations to help reduce predation:

A
  • Alarm calls, Mobbing predator (birds attacking predators)
  • Hiding, fleeing, forming herds/schools
  • Mechanical spines (porcupines)
  • Chemical excretions (skunks)
  • Aposematic (bright) warning colours (poison dart frog)
  • Cryptic colouration (camouflage)
  • Batesian mimicry (a palatable species mimics a not-so-good one)
  • Mullerian mimicry (two or more unpalatable species mimic each other, ie yellow jacket and cuckoo bee)
61
Q

Herbivory

A

is an exploitive +/- interaction in which an organism EATS a part of a PLANT or ALGAE

62
Q

Examples of herbivory:

A
  • Many are large animals such as moose, deer, cows, elephants, bears
  • Most are invertebrates such as snails, insects, beetles
63
Q

Like predation, herbivory affects…

A

the abundance of other species

  • Desert locusts can swarm and destroy vegetation, leaving severe economic loss of farmers
  • Sea urchins can wipe out productive kelp forests into ocean barrens
  • Beavers convert forest-bordered streams into ponds and open meadows, causing shifts in the species of vegetation present
64
Q

What do herbivores have?

A

specialised feeding adaptations

  • Chemical sensors to distinguish plant species and plant toxicity
  • Specialised teeth or digestive systems for processing different vegetation types
65
Q

Parasitism

A

is an exploitive +/- interaction in which an organism DERIVES NUTRIENTS from another organism (HOST)

66
Q

____of all species are believed to be parasites

A

~1/3

67
Q

Endoparasites (give example too)

A

live within the host

• Ex. Tapeworms

68
Q

Ectoparasites (give example too)

A

feed on the external surface

• Ex. Ticks and lice

69
Q

How do parasites do what they do?

A
  • Some parasites lay their eggs in a host and the larvae hatch and feed on the living host
  • Ex. Parasitoid wasps
  • Some later host behaviour
  • Ex. Acanthocephalan worms cause their crustacean hosts to leave protective cover and head into the open to be eaten
70
Q

What is the life cycle like for parasites?

A

Many parasites have complex life cycles (remember Apicomplexans?), requiring 2 or more hosts

71
Q

Parasitism significantly affect…

A

the survival of host populations
• Cause them to be weaker
- reduce reproductive output
- physical loss of features (ex fur/hair) making them susceptible to the elements

72
Q

Positive interactions influence…

A

community dynamics

73
Q

Positive interactions

A

(+/+ or +/0) occurs when at least one species benefits from the interaction and
neither is harmed

74
Q

Mutualism

A

is a positive +/+ interaction (not quite symbiosis but can be used synonymously)

75
Q

Examples of mutualism:

A
  • Nitrogen fixing bacteria in legume root nodules
  • Microorganisms digesting cellulose within the guts of termites and ruminant animals
  • Mycorrhizae
  • Endophytic fungi
  • Photosynthetic algae withing corals
  • Lichens!
76
Q

Obligate mutualists

A

CANNOT survive on their own and must associate with their mutualistic partner (ex.
lichens)

77
Q

Facultative mutualists

A

can survive without the mutualism, but benefit greatly from it
• Ie acacia-ant interaction -> will defend the tree in exchange for nectar and protective shelter

78
Q

What do positive interactions involve?

A
  • Involve the co-evolution of adaptations in both species, where changes in one species can affect the survival of the other
  • Ie Many flowering plants and specific pollinators
79
Q

Commensalism

A

is a positive +/0 interaction that only benefits one species but does NOT HARM either

80
Q

Why is commensalism difficult to document in nature?

A

because hard to discern the close association

  • Does the relationship really not harm or affect the species?
  • Ie hitchhiking algae on snail shells gain a new place to grow but many actually cause a very slight decrease in reproductive success in the snails….but is it counteracted by the addition of new camouflage?
81
Q

Where does commensalism often involve on?

A

Often involves on species obtaining food exposed by the other

  • Cattle egrets and cowbirds gain abundant food source when bison, cattle, etc disturb and flush out ticks and other insects
  • Following these animals provides the birds with ample food and little foraging effort
  • Can affect the cattle. Bison etc too…..birds wil sometimes each the ectoparasites directly off their bodies
82
Q

Facilitation (altruism)

A

is a positive +/+ or +/0 interaction where species may not have a direct contact in the symbiosis

83
Q

Example of Facilitation (altruism):

A

Ex Juncus gerardi makes the soil In salt marshes more hospitable, which other plant species can use later
• Shades the soil, preventing salt buildup due to surface evaporation
• Also transports oxygen to the soil
• Removing Juncus from the area resulting in a 50% decline in plant species present

biology (25 decks)

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