Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
24 Cards in this Set
- Front
- Back
Life history characteristics |
1.) Age & size at sexual maturity
2.) Amount & timing of reproduction
3.) Survival & mortality rates |
|
Natural selection |
favors individuals whose life history traits result in better chance of survival and reproducing |
|
Phenotypic plasticity |
describes how one genotype may produce different phenotypes (morphs) under different environmental conditions
changes in life history traits can result in changes in adult morphology (Ponderosa pines in different climates = different shapes) |
|
Polyphensim |
describes condition where a single genotype produces several distinct morphs (Spadefoot toad tadpoles have small omnivore morphs and larger carnivore morphs) |
|
Modes of reproduction |
1.) Asexual reproduction (cell division): prokaryotes and protists *some multicellular organisms reproduce sexually and asexually - corals*
2.) Sexual reproduction: fusion of male and female gametes |
|
Pros & cons of sexual reproduction |
PROS: recombination promotes genetic variation & better ability to respond to environmental change
CONS: individuals transmits half of its genome to next generation; population growth rate is slower |
|
Complex life cycles |
have at least 2 stages, with different body forms capable of living in different habitats
metamorphosis is an abrupt transition in form occurring between larval and juvenile stage
insects, marine invertebrates, amphibians, fishes, plants, algae, and protists |
|
Simple life cycles |
do not have abrupt transitions
vertebrates |
|
Semelparous |
species reproduce only once
agave, giant Pacific octopus, annual plants |
|
Iteroparous |
reproduce multiple times
pines/spruces, large mammals |
|
r-selection |
r = rate of increase of population
high population growth rate; advantage in uncrowded conditions
short life spans, rapid development, early maturation, low parental investment, high reproduction rates
insects, small vertebrates, weedy plants |
|
K-selection |
K = carrying capacity for population
slower growth rates; advantage in crowded conditions
long-lived, develop slowly, late maturation, invest in each offspring, low reproduction rates
large mammals, reptiles (tortoises and crocs), long-lived plants (oak and maple trees) |
|
Grime’s classification |
focuses on plant life histories
based on habitat stress (abiotic factors limiting growth) and disturbances (processes destroying biomass) |
|
Low stress / Low disturbance |
competitive plants
superior ability to acquire light, minerals, water, and space
have selective advantage
|
|
High stress / Low disturbance |
stress-tolerant plants with phenotypic plasticity
slow rates of water and nutrient use
defenses to herbivores |
|
Low stress / High disturbance |
ruderal plants
short life span
rapid growth rates
heavy investment in seed production
opportunistic |
|
High stress / High disturbance |
not suitable for plant growth |
|
Charnov approach |
examine and compare life history traits by removing influence of size and time
divide species’ average age of maturity by average life span = dimensionless ratio (c)
dimensionless ratio allow comparisons of different life histories
c differs between ectothermic and endothermic animals (takes fish and lizards longer to mature than mammals and birds) |
|
Trade-offs |
organisms allocate limited energy/resources to one function versus another |
|
Trade-offs of different life histories |
size vs. # - larger investment in each offspring means fewer offspring produced
in species w/o parental care, resources are invested in propagules (eggs/seeds)
size of propagules is trade-off with # produced |
|
Trade-offs between current / future reproduction efforts |
some iteroparous organisms - earlier it reproduces, the more times it can reproduce in lifetime; trade-off of # of offspring increases with size & age of organism
advantages in delaying reproduction and investing more energy in growth and survival (a fish with 5-yr lifespan can increase total reproductive output by delaying maturation by 1 yr.)
BUT if adult survival rate is low, future reproduction may never occur; early reproduction would be favored |
|
Senescence |
decline in physiological function with age
onset can set upper age limit for reproduction
semelparous species undergo rapid senescence and death following reproduction |
|
Different selection pressures at different life cycle stages |
as selection pressures change, different morphologies and behaviors can be adapted at different life stage cycle stages
small early life stages often vulnerable, small size weakness offset because early stages can do things/have abilities that adult stage does not *parental investment: provisioning eggs/embryos with yolk and protective covering for eggs and parental care —> lessens early pressures
*dispersal: small offspring well-suited for dispersal —> reducing competition and allowing increased colonization of new areas or escaping from diseased/high predation areas (plants, fungi, marine invertebrates)
*dormancy: state of suspended growth and development so organism can survive unfavorable conditions (small seeds, spores) |
|
Justification for complex life cycles |
Functional specialization of stages is a common feature
Insects: larval stage stays in small area and larvae are specialized for feeding and growth; adults specialized for dispersal and reproduction
Marine invertebrates: larvae specialized for feeding and dispersal in ocean currents and have structures to deter predators |