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BIO120 > 23/24 > Flashcards

23/24 Flashcards

1
Q

primary producers

A

plants

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2
Q

primary consumers

A

herbivores

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3
Q

secondary consumers

A

carnivores who eat herbivores

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4
Q

tertiary consumers

A

carnivores who eat secondary consumers (predators)

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5
Q

decomposers

A

eat dead organic matter

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6
Q

what does the pyramid shape represent?

A

decreasing biomass in higher trophic levels

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7
Q

describe indirect effects in food webs/chains and give an example

A
  • one species alters the effect that another species has on a third
  • eg exploitative or scramble competition, if the contested resource is a species
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8
Q

trophic cascades: HSS

A

interactions between two trophic levels cascade to a third trophic level

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9
Q

why is the world green?

A
  • Hairston, Smith, Slobodkin (1960) proposed the green world hypothesis
  • states that carnivores keep down herbivores so herbivores don’t limit plant growth
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10
Q

how is the green world hypothesis an example of an indirect effect?

A

one trophic level exerts influence on a second by affecting a third

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11
Q

top down control

A

abundances kept low because of predation
- experimental test = predator removal

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12
Q

bottom-up control

A

abundances kept low because of resource limitation
- experimental test = resource addition

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13
Q

solid lines for trophic cascades

A

direct effects

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14
Q

dashed lines for trophic cascades

A

indirect effects

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15
Q

compare indirect and direct effects

A
  • indirect effects can be as strong as direct effects
  • outcomes are not fundamentally predictable; this depends on interaction strengths
  • experiments are needed (perhaps long term)
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16
Q

where does much biodiversity reside?

A

plants and insects

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17
Q

why are there so many species of insects and plants?

A
  • Coevolution
  • Niche specialization
  • Rapid reproductive cycles
  • Habitat diversity
  • Polyploidy in plants
  • Metamorphosis in insects
  • Geographic and climatic stability
  • High mutation and adaptation rates
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18
Q

difficulties of herbivory as opposed to carnivore

A
  • animal tissues are easy to convert into animal tissues
  • plant tissues are hard to convert into animal tissues
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19
Q

3 difficulties of plant tissues

A
  • cellulose and lignin are tough and indigestible without microbial symbionts
  • plant tissues are heavily defended against herbivores
  • coevolutionary race between plants and insect herbivores is responsible for much of biodiversity: specialisation is common
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20
Q

example of plant defences against herbivores

A

milkweeds exude distasteful white sap if damaged
- most generalist insects can’t eat milkweeds, but specialists can evade defences
- milkweed-feeding specialist monarch butterfly larva cut leaf midrib to reduce sap pressure before eating
- caterpillars don’t detoxify the poison, but sequester it in their cuticle, making themselves poisonous and distasteful

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21
Q

brightly coloured insects

A
  • frequently toxic
  • warning coloration
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22
Q

plant-herbivore interactions as an arms race

A
  • plants evolve toxins to reduce herbivory; insects evolve detoxification or other mechanisms to overcome plant defences
  • many types of secondary chemicals (esp alkaloids) often deter generalist herbivores
  • no plant species is toxic enough to escape from specialist herbivores
  • specialist insects may evolve to use defence chemicals as feeding stimulants or defence compounds

result: escalation, arms race!

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23
Q

why do we think plants taste ok?

A

our food crops have been selected for low toxicity

24
Q

how are plant defensive compounds important to humans?

A
  • many plant secondary chemicals have diverse, potent biological activities
  • some alkaloids are important to us
25
Q

examples of useful alkaloids for humans

A

coffee - caffeine
coca - cocaine
tobacco - nicotine
opium poppy - morphine

26
Q

in what ways are challenges and solutions different for vertebrate herbivores?

A
  • Many insects complete development on a single, often well-defended plant; they must overcome plant defences
  • Vertebrate grazers often eat some plant tissue, and then move on to another plant
  • Vertebrate herbivores often select mixed diets containing foods processed by different
    detoxification pathways, thereby avoiding high doses of any one toxin
  • Some detoxification by microbes in fermenting chambers
27
Q

rumen

A

foregut

28
Q

cecum

A

hindgut

29
Q

what produces unlimited diversification?

A

physical environment isn’t complex enough to produce extraordinary species diversity
interactions with other organisms do this

30
Q

why do plants around a pond with fish get better pollination and bees?

A

there are fewer dragonflies

31
Q

two examples of complex networks of species interactions in ecological communities

A
  • parasite-herbivore-plant network (Costa Rica)
  • plant-pollinator network (Greenland)
32
Q

why do lizards benefit plants?

A

because of unequal interaction strengths:
- effect of lizards on spiders is week
- effect of lizards on herbivores is strong
- lizards reinforce the effect of spiders

33
Q

lizards eat

A

spiders and herbivores

34
Q

spiders eat

A

herbivores

35
Q

what do Anolis lizards eat?

A

spiders and beetles

36
Q

Spiller and Schoener 1992

A

replicate Caribbean islands; remove Anolis lizards

37
Q

major threats to biodiversity

A
  • habitat destruction
  • overexploitation
  • invasive species
  • pollution
  • climate change

often have synergistic effects

38
Q

what four things can result from environmental change?

A

acclimation, adaptation, range shifts or extinction

39
Q

give 4 examples of changes to the environment due to humans

A
  • ice disappearing
  • forests cut down
  • primates sold as pets or bushmeat
  • mercury put in rivers
  • microplastics
40
Q

effects of increasing atmospheric CO2 levels in the last century

A
  • human activities adding more CO2
  • intensifies greenhouse effect and causes global warming
  • global temperature has increased dramatically
41
Q

how is climate changing other than temperature?

A
  • circulation patterns are changing: Hadley cells get stronger and therefore larger, causing desert belts shifting poleward beyond 30 degrees
  • extreme weather events becoming more frequent
42
Q

what happens to organisms as the climate changes?

A

acclimatisation through phenotypic plasticity
adaptation to new conditions
range shift migration to suitable conditions
extirpation, which is global or local extinction

43
Q

acclimation

A

Early or gradual exposure to environmental stress can reduce its negative impacts
- Porcelain crabs (Petrolisthes) acclimated
to cold temperatures function better at colder temperatures
- But acclimation to warm temperatures increases high-temperature tolerance only minimally

44
Q

give an example of how climate change is more than just the direct effects of warming

A

Snowshoe hares (Lepus Americans) are white in winter and brown in summer
Coat colour is important for reducing predation, and white animals are conspicuous against a snowless background

45
Q

Mills et Al.

A
  • studied snowshoe hares in western Montana over 3 consecutive winters
  • radio-collared hares and performed weekly measurements of coat colour and snow around each hair
  • wanted to determine whether there I sufficient, current plasticity in the initiation or rate of coat colour change to reduce mismatch and respond to changes in snow cover
46
Q

Mills et Al. results

A
  • it is getting cooler later in the fall and warmer earlier in spring
  • in general, snow is arriving later and leaving earlier
  • there is little variation in fall coat change; there is more variation in spring coat change
47
Q

so, will plasticity alone in coat colour change able to respond to changes in conditions?

A

No, there is not enough plasticity to avoid mismatches
- projections of future snow duration show there will be greater mismatch between snowshoe hare coat colour and its background

48
Q

how is coat colour mismatch predicted to affect hare population growth?

A

predicted to slow it

49
Q

so, will hares adapt?

A

open question; depends on the amount and type of genetic variation underlying the timing of coat colour change

50
Q

range shifts

A
  • species moving polewards
  • also up mountains
51
Q

give an example of an animal that can’t go up mountains

A

pikas; death zone at low altitude

52
Q

the Great Basin

A

many small mountain ranges, green ‘sky islands’ in a matrix of desert

53
Q

are pikas threatened by climate change?

A

The elevational range of American pikas in the Great Basin is getting smaller
- Sites where pikas have gone locally extinct often had temperatures above 26°C, which can be lethal to pikas (if they cannot behaviourally thermoregulate)
- The American pika was under consideration to be listed as an endangered species in the US (but the US ultimately decided against it)
- On the other hand, American pika populations in the Rocky Mountains and elsewhere appear to be healthy
(Smith et al. 2020)
- In Canada, the Collared pika (which lives in the Yukon, Northwest Territories, and BC) is federally designed as a species of “Special Concern’

54
Q

example of landscapes defeating migrations

A

Pronghorns can run but not jump. Whole herds have been killed at fences in the winter

55
Q

is extinction reversible

A

no

56
Q

most extinction models ignore

A

many factors thought to be important in determining future extinction risks such as species interactions, dispersal differences, evolution

BIO120 (61 decks)

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