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Ecology > Lec 7 > Flashcards

Lec 7 Flashcards

1
Q

Life history

A

Organism’s sequence of events relating to its birth, growth, development, reproduction, senescence (getting old), and death

INDIVIDUAL

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2
Q

Life History Strategy

A

Species’ overall pattern of life history events exhibited by all organisms within the species

POPULATION

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3
Q

Questions for life histories

A

How fast to grow and develop?

When to metamorphose?

How fast to grow?

How large to grow?

When to begin reproducing?

How many offspring and of what size?

How often to breed?

Whether to care for offspring?

How long to live?

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4
Q

Trade-offs of Life-Histories

A

Organisms allocate limited energy and resources to one structure or function at the expense of another

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5
Q

_____________ does the selecting in natural selection

A

ENVIRONMENT

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6
Q

What shapes and constrains life-history evolution?

A

Trade-offs

A life history maximizes an individual’s fitness and a lige history strategy adapts a species to its environment

These are NOT conscious decision-making events - they occur because they have been selected for

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7
Q

There is a ________ range of body sizes

A

LARGE

Mammals range from pygmy shrews (2g) to blue whales (80,000,000g)

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8
Q

Large animals tolerate _____________ best while small animals tolerate ________ best

A

COLD environments; WARM environments

SIZE trade-off

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9
Q

Large trees are less susceptible to ________ than small trees but are more susceptible to _______

A

FIRE; WIND

SIZE trade-off

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10
Q

Age at First Reproduction:

Allocating resources to reproduction takes resources away from:

A

Growth, maintenance, and defense

The cost of reproduction is therefore REDUCED survival, growth, and future reproduction

Age at 1st reproduction trade-off

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11
Q

Precocial

A

Species reproduce at a very EARLY age (i.e. mayflies)

INCREASE fitness quickly in population, but DECREASE survival and future reproduction

Age at 1st reproduction trade-off

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12
Q

Altricial

A

Species reproduce at a much LATER age (i.e. humans)

Fitness does NOT increase quickly, survival and future reproduction INCREASED

Age at 1st reproduction trade-off

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13
Q

Number of Reproductive Events: Semelparous

A

Reproduce ONE TIME ONLY (i.e. salmon, mayflies, annual plants, agave/century plants)

Trade-offs:
-Invest too many resources in reproduction to be able to survive afterwards

-Increase fitness by saving up resources over time and producing the highest quality offspring all at once

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14
Q

Number of Reproductive Events: Iteroparous

A

Reproduce several times (i.e. most trees, birds, mammals)

Trade-offs:

  • Produce offspring without completely depleting resources
  • INCREASE fitness by producing more frequently
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15
Q

Number and Size Offspring Trade-offs

A

An organism’s energy investment in its offspring can be measured by the size of the offspring

The larger an organism’s energy investment in each individual offspring, the fewer offspring it can produce

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16
Q

Parental Care: Trade-offs

A

Energy investment can also be measured by the amount of parental care provided

Organisms that provide parental care INCREASE the chances of their offspring surviving

However, they can produce far FEWER offspring

17
Q

Metamorphosis

A

Complete rearrangement of an organism’s body plan during its lifetime

I.e.:

  • Insects: eggs -> larvae -> pupae -> adults (butterflies and moths
  • Amphibians: eggs -> tadpoles -> adults (frogs and salamanders
18
Q

Metamorphosis: Advantages

A

Using different food sources and exploiting different habitats minimizes COMPETITION between the young and adults of a species

Larval forms are usually small and excellent as DISPERSING (via water or wind) to colonize new habitats

19
Q

Metamorphosis: Disadvantages

A

Complex genetic task to reorganize body plan

Energetically VERY costly

20
Q

Life cycles

A

Life histories of organisms often go beyond metamorphosis to include complex life cycles

Examples:

  • Multiple hosts in the life cycle of a parasitic worm
  • Both sexual and asexual reproduction in the life cycle of corals
21
Q

Plant life cycle

A

Alternation of generations

  • DIPLOID sporophyte produce HAPLOID spores by MEIOSIS, which grow into HAPLOID gametophytes by MITOSIS
  • HAPLOID gametophytes produce HAPLOID gametes by MITOSIS, which undergo fertilization to form DIPLOID zygotes, which grow into DIPLOID sporophytes by MITOSIS

Same-> same: MITOSIS
Like-> Unlike: MEIOSIS

22
Q

Resting stages

A

Resistant or inactive stages during periodic unfavorable conditions

Includes torpor, hibernation, diapause, and estivation in animals

  • Dormancy in plants (seeds, winter or drought deciduous)
  • -Annual plants

Trade-offs:
-Resting stages postpone immediate reproductive success and fitness for future (hopefully better) reproductive success and fitness

23
Q

Longevity

A

Large range of lifespans in all groups of organisms
–Plants can live a few days (some annuals) to 5000+ years (bristlecone pines/Methusila)

TRADE-OFFS:

  • Shorter lifespan = early mortality but SHORT generation times
  • Natural selection acts FASTER to more quickly adapt short-lived species to environments
24
Q

Putting it all together

A

Robert MacArthur and Edward O. Wilson developed a classification scheme for life histories in 1967
–r-selected strategies vs. k-selected strategies

25
Q

r-selected species

A
  • SMALL size
  • EARLY maturity/reproduction (PRECOCIAL)
  • MANY SMALL offspring
  • LITTLE parental care
  • SHORT generation times
  • SHORT lifespan/EARLY mortality
  • Habitats are FREQUENTLY DISTURBED

EXAMPLES:
–Most insects, small vertebrates (i.e. mice), and annual plants

26
Q

k-selected species

A
  • LARGE size
  • LATE maturity/reproduction (ALTRICIAL)
  • FEW LARGE offspring
  • MUCH parental care
  • LOND generation times
  • LONG lifespan/LATE mortality
  • Habitats are CONSTANT and PREDICTABLE

EXAMPLES:
–Large mammals (i.e. elephants), large reptiles (i.e. tortoises and crocodilians), and large trees (i.e. oak)

Ecology (13 decks)

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