7.12. (10/7) Life Histories

Question 1

How many offspring does an organism produce that live to reproduce?

Answer 1

on average, one

Question 2

What are life histories?

Answer 2

Attributes of the schedule of an individual’s life

Question 3

What are the different ways an organism produces one offspring that lives to reproduce?

Answer 3

• salmon go far to lay thousands of eggs, then dies
• elephant has one baby every several years (lots of energy to protect and care)
• loggerhead sea turtle buries dozens of eggs and leaves them to fend for themselves
• female mayfly lays 50-10k eggs as an adult for one day, then dies

Question 4

what is age at maturity?

Answer 4

age of first reproduction

Question 5

what is parity?

Answer 5

number of reproductive events

Question 6

what is fecundity?

Answer 6

number of offspring produced per reproductive episode

Question 7

What are life history traits?

Answer 7

• fecundity
• parity
• age of maturity
• size of offspring
• life span and aging

Question 8

How does natural selection affect life histories?

Answer 8

• reproductive success depends on life history traits which influence evolutionary fitness
• they vary with respect to environmental factors/ habitats

Question 9

what is the principle of allocation?

Answer 9

organisms have finite amounts of energy that they have to choose how to use because it affects each area differently
* reductions and trade-offs
* weigh potential costs of varied production

Question 10

How does resource allocation affect fitness?

Answer 10

• increased seed production may lead to more offspring
• seed size is reduced in order to make more which could affect their survival as seedlings
• more energy is used to produced seeds rather than making roots for an adult tree which affects survival
• so much energy spent now can affect future seed production

Question 11

Who has the largest seed? smallest?

Answer 11

• double coconut: few seeds of ~50 pounds
• spotted coralroot orchid: billions of seeds of ~0.000002 g

Question 12

what kind of relationship exists between seed size and seed number?

Answer 12

there is a negative relationship between seed size and seed quantity where the smaller number of seeds produced yields a bigger size and the smaller the seed the more are made

Question 13

When is it advantageous to produce a large number of small seeds?

Answer 13

areas with high disturbance

Question 14

When is it advantageous to produce a small number of large seeds?

Answer 14

in stable environments with lots of plant biomass and competition because each is more capable of surviving environmental hazards

Question 15

What causes variations in maturity age?

Answer 15

When the chances of an organism surviving to adulthood is low they use a lot of energy to reproduce at a younger age, but if they do survive, they wait until they have enough energy to reproduce (they also invest less resources for reproduction)

Question 16

What is the trend for species that have high mortality/short lives?

Answer 16

they have a higher fecundity

Question 17

what are semelparous organisms?

Answer 17

organisms that only reproduce once and die
* big bang

Question 18

What are iteroparous organisms?

Answer 18

reproduce multiple times in their life

Question 19

How are life histories classified?

Answer 19

they are based of population characteristics of fecundity, survival, relative offspring size, and age of reproductive maturity

Question 20

what is mx?

Answer 20

fecundity

Question 21

what is Ix?

Answer 21

survival

Question 22

By who and when were r and K selection defined

Answer 22

By MacArthur and Wilson in the 1960s

Question 23

what are r selection species?

Answer 23

Favors high potential population growth rate in species that colonize new or disturbed habitats

Question 24

what are K selection species?

Answer 24

Favors those that are good at attaining resources and maintain their populations at carrying capacity

Question 25

What is distinct about the r and K selection definition?

Answer 25

This definition exists at the ends of a continuum and relates population dynamics to their environment

Question 26

what are characteristics of a r selection species?

Answer 26

- high population increases - bad competitor - rapid development of life stages - early reproduction with one event (semelparity) - small body size with many small offspring

Question 27

what are characteristics of a K selection species?

Answer 27

- competitive - low population increases - slow development - late reproduction many times (iteroparity) - large body size

Question 28

What are two species that represent r and K selection well?

Answer 28

mice as an r selection species and elephants as K (for mammals)

Question 29

What is the Grime's Scheme?

Answer 29

states that intensity of disturbance and stress are the two important variables that affect the life history characteristics of *plants*

Question 30

What does intensity of disturbance mean?

Answer 30

how intense and limiting the periodic process of biomass removal was for plants

Question 31

what does intensity of stress mean?

Answer 31

how much external pressure and constraint limits rate of growth * examples include nutrient poor, extreme weather

Question 32

what are the three kinds of habitats according to Grime's Scheme?

Answer 32

1. low disturbance-low stress 2. low disturbance-high stress 3. high disturbance-low stress (form a triangle)

Question 33

Who are the competitors?

Answer 33

- they are at the top of the grime's scheme triangle with low disturbance and low stress - lots of plants grow here so they compete for available resources

Question 34

Who are the stress tolerators?

Answer 34

- they are on the left side of grime's scheme triangle with low disturbance and high stress - high background stress like deserts

Question 35

who are the ruderals?

Answer 35

- they are on the right side of grime's scheme triangle with high disturbance and low stress - they are good at occupying habitats that are disturbed (lawns)

Question 36

what are the characteristics of stress tolerators?

Answer 36

- limited resources - allocate/conserve resources to defense, maintenance, adaption - grow slowly - vegetative/asexual reproduction - variable life form - leathery, needles leaf form - evergreen leaves - late reproductive maturity - slow potential growth rate - long longevity - low proportion of energy used to make seeds - vegetative reproduction is often important

Question 37

what are the characteristics of ruderals?

Answer 37

- colonize disturbed habitats - rapid growth - invest a lot of resources/energy to reproduction - mature quickly - produce many seeds (easily dispersed) - r strategists - herb life form - variable leaf form - herbaceous life form - variable leaf form - deciduous leaves - early reproductive maturity - rapid potential growth rate - short longevity - high energy invested in seed production - vegetative reproduction is rarely important

Question 38

what are the characteristics of competitors?

Answer 38

- grow rapidly large - allocate energy toward early growth - good at obtaining resources - long lifespan - variable life form - variable leaf form - variable life form/leaf form - deciduous leaves - late reproductive maturity - fast or slow potential growth rate - moderate to long longevity - low energy for seeds - vegetative reproduction is sometimes important

Question 39

what is phenology?

Answer 39

timing of biological events that are playing out over a year - when a particular species leaf out, set flower, set seed

Question 40

who is Aldo Leopold? What was discovered because of him?

Answer 40

- In the 1930s and 40s, he kept a notebook about the timing of flowering and spring bird events - advancement of spring events

Question 41

Why does changing phenology matter?

Answer 41

if all species started their activities earlier there would be no problem, but since only some species are shifting, it disrupts important ecological interactions for dependent species