BIOL 2300 Lecture Notes - Lecture 9: Agave Americana, Size Small, Capelin

22 views8 pages
LECTURE 9 LIFE HISTORY
Life History
Life History Trade-off: Growth & Survival VS. Reproduction
Organisms may adopt different strategies over evolutionary time.
Life history traits
Which strategy evolves depends on environmental conditions
1. How often to breed?
2. How many offspring to produce in each breeding event?
3. When to begin reproducing?
Life History Classifications
Summary
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in
2
Life History
Resources are often limited…
o Organisms must decide how to allocate time/energy to different
activities throughout lifespan
o Allocation decisions will affect an individual’s fitness – by influencing
growth, reproduction and survival
Trade-off between growth and survival with reproduction
Reproduction takes a lot of energy
Therefore, organisms will develop allocation strategies over evolutionary time
to adapt to abiotic and biotic conditions in their environment
Trade-off Increased allocation of time/energy to some activities results in a
decreased allocation to other activities
o Increase in one thing means a decrease in something else
Life History Trade-off: Growth & Survival VS. Reproduction
Mainly concerned with…
Reproductive effort: the proportion of available resources that an individual
allocates to reproduction throughout its lifespan
o Current + future reproductive output
o Future reproductive output = survival + fecundity in the future
o Fecundity: number of offspring produced/event
Lifetime Reproductive Success: the number of offspring produced
throughout the lifespan of an individual
o Similar to fitness but not does not involve the offspring surviving to
reproductive age
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in
3
Organisms may adopt different strategies over
evolutionary time.
Life History Strategy: set of choices and decisions resulting in an individual’s
allocation to reproductive effort through its lifespan
For example:
1. Invest heavily in current reproduction
o May drain a parent’s energy reserves
o Reduce ability to grow → lower probability of survival
o If survive, may produce fewer offspring in the future
2. Invest heavily in current growth/survival (delay reproduction):
o Faster growth → higher probability of survival
o Larger size more resources available for future reproduction
The optimal strategy will be a compromise between the allocation of
time/energy to growth/survival versus reproduction.
Life history traits
Body size / growth
o Fecundity increase with body size
Age at sexual maturity
Number of reproductive events parity
Number of offspring produced per event fecundity
Offspring size
Amount of parental care
Senescence, programmed death termination of life
A life history strategy integrates all of these traits in a way that maximizes
fitness.
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Life history trade-off: growth & survival vs. reproduction. Organisms may adopt different strategies over evolutionary time. 3: because the strategy influences an individual"s fitness, the strategy will be molded by natural selection over evolutionary time. Agaves (the century plant : inhabit climates with erratic rainfall, plants store nutrients and grow for several years (average life span ~ If iteroparous: general pattern: as more offspring are produced the survival of each offspring decreases, fewer offspring allocate more resources per offspring, more offspring allocate less resources per offspring. 6: but do not delay too long, most organisms experience senescence: gradual increase in mortality and decline in fecundity with age. 7 r large reproductive allocation but invest little in survival: k large allocation to survival but little in reproduction, strategies fall along a continuous spectrum between r- and k- selection (both within and among species.

Get access

Grade+20% off
$8 USD/m$10 USD/m
Billed $96 USD annually
Grade+
Homework Help
Study Guides
Textbook Solutions
Class Notes
Textbook Notes
Booster Class
40 Verified Answers
Class+
$8 USD/m
Billed $96 USD annually
Class+
Homework Help
Study Guides
Textbook Solutions
Class Notes
Textbook Notes
Booster Class
30 Verified Answers

Related Documents

Related Questions