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BIO120 > Lecture 18 > Flashcards

Lecture 18 Flashcards

1
Q

T/F the population grows fast when it is small in a logistic model

A

true
most of the resources are available
doesn’t happen irl

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2
Q

T/F the pop grows slowly when it is large in a logistic model

A

true
run out of resources
doesn’t happen irl

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3
Q

Allee Effects

A

when the pop decreases when the population size or density is low
- difficulty finding mates, group defence, group living = social benefits
- cooperative behaviours become ineffective when the pop size is too small
when allee effects are too high - the pop will not be able to grow past a certain lower limit

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4
Q

why do meerkats need a minimum population density to grow

A

they cooperate in groups of 6 to avoid predators - so they need a minimum number of individuals to create these groups to survive

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5
Q

T/F exponential and logistic models do not include allee effects and treat all individuals in a population the same

A

true
not realistic
not all individuals have the same probability of giving birth or dying

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6
Q

what is fecundity

A

the number of offspring an individual can produce over a given period
- reproductive capacity of an individual, of a population
- depends on age, health, environmental conditions
- it is the biological POTENTIAL for reproduction - not fertility which is the actual number of children born

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7
Q

what is survivorship (lx)

A

the probability that an individual will survive from birth to a given age
- 3 different types of survivorship curves
- age, predation, disease, resource availability = factors that affect survivorship
(older age = less survivorship)

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8
Q

what is the typical life history for many plants and animals

A
  1. start life = small size
  2. grow without reproducing, resource accumulation - gather resources
  3. when enough accumulation of resources + sexually mature, start spending resources on reproduction (some reproduce at once - die, some reproduce periodically)
  4. need to consider the age structures of the population to predict the population better
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9
Q

an elephant has ___ fecundity and spends ___ of investment on one offspring at a time

A

low fecundity
a lot of investment
becomes sexually mature later on in life
has 1 offspring –> wait –> 2 offspring

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10
Q

a pika has ___ fecundity and spends ___ of investment on offspring

A

high fecundity (1-13 offspring at a time)
medium lifespan
very fast reproduction, within the first year of living = sexually mature
invests a little in the offspring

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11
Q

a salmon has ____ fecundity and invests ___ of an investment in offspring

A

very high fecundity (thousands of eggs)
invests very little in each egg
very late reproduction maturity, waits till the end of its life to reproduce –> die

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12
Q

explain how a population without and with age structure would be classified

A

without age, the structure would be 24 individuals in a population with no in-depth classification
with age structure = categorizing based on fecundity and survivorship into babies, children, young adults, and elderly
- ecologists = women as the only reproduction because they invest in it more, men = cheap sperm

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13
Q

what are arbitrary units of time

A

chosen to give a reasonable number of age classes for an organism
- microbes = minutes
- insects = weeks
- mammals = years

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14
Q

what are life tables

A

a statistical tool used to summarize the survival and reproduction pattern of a population
- things that are expected of the average individual of a certain age

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15
Q

what are survivorship schedules

A

lx = probability of being alive at the age x
l0 = 1.0 when a child is born and is always declining
graph of lx against x = age

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16
Q

what are the types of survivorship curves

A

Type 1: high survivorship early and a steep decline later
- survive through early and middle life - the mortality increases significantly with age
- humans, live to old age, infant mortality is low, and large mammals
Type 2: straight diagonal line
- the chance of dying at any age is the same
- birds and small mammals = predation and high risk of disease
Type 3: concave up curve and flattens as the age increases
- the majority of individuals die in early ages - eggs, larvae, seedlings
- survivors in adulthood face lower mortality rates
- fish, plants - lots of eggs and seedlings but they do not all survive

17
Q

fecundity schedules

A

tables or representations that describe the reproductive output of individuals at different ages or stages of their life
- mx or bx
- the curve of fecundity should increase around 20-35 years old = sexual maturity = more potential for more daughters
- the curves vary widely among species - usually genetically determined

18
Q

fecundity-survivorship tradeoffs

A

refers to the balance organisms must have between investing energy and resources in reproduction and ensuring the survival of themselves and their offspring
- must learn to allocate resources efficiently

19
Q

what is the net reproductive rate (R0)

A

the average expected number of daughters a female has in their lifetime
R0 = sigma lx * mx
mx = total number of daughters produced by a mother who doesn’t die early, multiplying it by the probability that some mothers do die early
- units of one generation, not one-time interval

20
Q

Net reproductive rate (R0) in the news

A

R) is the average number of secondary infections that a single infection gives rise to
- every daughter that is made gives rise to another daughter

21
Q

How can we model the time at which a female gives birth

A

T = sigma x * lx * mx / R0
* a formula you have to remember
- this formula = weighted average
x = female age
multiplying the 2 terms together = time

22
Q

what are the tradeoffs to reproduction

A

reproduction = costly
longer pre-reproductive periods allow time to accumulate more resources

23
Q

semelparous organisms

A

big bang
organisms that reproduce all eggs at one period of time –> die
salmon, at the end of life
plants that reproduce, annual, biennial or monocarpic perennial (all monocarpic plants = die after reproducing once)

24
Q

iteroparous organisms

A

humans, elephants, pikas
organisms reproduce multiple times over their lifetime, producing fewer offspring per event
plants = perennial

25
Q

why does natural selection favour semelparity

A

when reproductive output is increased by accumulating resources for longer
plants that = more fruits = more beneficial to attract pollinators or seed dispersed = preparation for reproduction
they want to produce more flowers and fruits to maximize their single reproductive period of time
*NS favours semelparity because they take the time to maximize their fitness as a strategy

26
Q

what is the advantage of synchrony in semelparity

A
  • some plants like bamboo synchronize the semelparity
  • producing more seeds at once reduces the likelihood that all seeds will be eaten by predators (PREDATION SATIATION TACTIC)
  • masting = sometimes no seeds, sometimes a lot of seeds
27
Q

what is the K strategy

A

focuses on producing fewer offspring and investing heavily in their survival, maintaining populations near the carrying capacity (K) of the environment.
- slower growth
- lower reproductive rate
- poor at dispersal
- longer generation time
- iteroparity more likely - more offspring with more time

28
Q

what is the r strategy

A

The r-strategy emphasizes rapid reproduction and high fecundity to maximize the growth rate (r) of a population
- faster growth
- shorter generation time
- higher reproductive rate
- good at dispersal
- semelparity = more likely - one reproductive

29
Q

T/F selection generally selects for early reproduction but the need to accumulate resources and size-dependent mating success can override that effect = delayed reproduction or semelparity

A

true

30
Q

T/F semelparity selects for synchrony

A

true
more seeds at once = less eaten by predators

31
Q

what is ex

A

life expectancy
- the expected years of life left to live in an individual of age

32
Q

what is vx

A

the reproductive value
- the expected number of future daughters left to an individual of age x
- this is good for breeding - males only like females with high vx = highest reproductive value offspring
- the graph = upside down parabola
- maximum vx = in late teens as they enter reproductive years
increase age = decrease reproductive success

BIO120 (29 decks)

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