Lecture 9 life history - Steven Pennings PDF

Preview

Summary

Steven Pennings...

Description

Lecture 9 life history Tuesday, February 9, 2021

5:40 PM

All organisms reproduce, but the way they do it varies trem Sequential hermaphroditsm: changes in sex that happen fo Simluatneous hemaphroditism: being two sexes at the same Life history: pattern of trowth, development, reproduction its time between these things ○ Defined by age & sex at sexual maturity ○ Amount & timing of reproductiong ○ Survival & mortality rates • Different approaches to life history reflect various fitnes • Life history patterns vary within and amongst species ○ Variation within a species is usually less than variation ○ Variation within a species: § Phenotypic plasticity: one genotype - different phe □ Sometimes produces distinct phenotypes or m □ Allometry: differences in the growth rates of different rates, causing differences in shape ○ Variation among species: § Variations in sexual & asexual reproduction § Sexual reproduction has a lot of benefits, the bigg so it yields genetic variation □ The main disadvantage is that the male and fe matieral - only half of the genome is transmitt □ Isogamy: two equally sized gametes that have • • • •

endously reproduction (like what happens in clownfish) time & survival; how an individual organism divides

trade offs among species notypes under different conditions rphs - polyphenism the body parts; different body parts grow at

est one being that it recombines the genotype male only contributes half of the genetic ed to the offspring two mating types fusing

□ Isogamy: two equally sized gametes that have □ Anisogamy: the gametes are different sizes; s difference in size is more costly in terms of r limited supply □ Semelparous: reproduce once in their life ® Annual plants ® Giant pacific octopus ® Advantage is all energy is spent towards g resources is invested in reproduction □ Iteroparous: reproduce multiple times ® Trees ® Most large mammals ® Able to have "multiple chances" at reprod □ It may be physiologically impossible for some ○ Complex life cycles have at least two disstinct stages, different habitats § If there is an abrupt transition between said stag transition from larval to juvenile stage § 25 of 33 animal phyla have complex life cycles, inc amphibians, most fish, and more. § Different life stages have different traits and th □ Parents and offspring and be subjected to var ® This is beneficial as it allows the two dist which avoids trade-offs that plague life h § Although most organisms have complex life cycles stage □ Direct development: loss of the larval stage (e

two mating types fusing tuation for most multicellular organs; the production which is why female gametes are in

owth and then the rest of the life force and

ction if one season is worse than another pecies to effectively be semelparous may have different body forms and live in s, then it is called metamorphosis: abrupt uding insects, most marine invertebrates, s can perform different tasks ying selection pressures nct stages to evolve in totally different ways, story decisions there are some that have lost one or the other g. tree frog not having tadpole babies, instead

having eggs that hatch into tiny baby frogs) □ Metamorphosis/neotny: group with complex lif the individual becomes sexually mature while m axolotls) § Plants and algae also have complex life cycles wher composition - one being diploid (sporophyte) & one □ Tremendous variability in the altneration of ge ○ humans have a simple life cycle where there is no abru • Life history theory: ○ R-k describe two ends of a continuum of reproductive § Terms derive from mathematical terms of populat § "r": intrinsic rate of increase of a population □ High population growth rates in an uncrowded § K: the carrying capacity for a population □ The ability to compete in a crowded environme □ Slower growth, more efficient reproduction, g § Individual species would be placed somewhere alon § R & k traits cannot both be maximized as they ten ○ CSR triangle: proposed by JP Grime who argued that p defined as anything that hindered growth § Plants were also affected by distubrance which he biomass § Grime believed that plants could not survive if bot argued that there were only three combinations in distubrance - low stress, low distubrance - low str

e cycles and the adult stage is abandoned so aintaining a larval body shape (e.g. salamanders, e the two stages alternate in their genetic being haploid (gametophyte) nerations t transitions atterns on growth r newly disturbed habitat nt od competitive ability g a continuum from r to k selected d to be opposite traits ant growth was limited by stress which he defined as any process that destroyed plant h stress and disturbance levels were high so he nature: low disturbance - high stress, high ss

§

□ Diff traits would occupy diff areas of the tria ® Upper point of the triangle is characteriz ◊ Plant growth is not limited by abiotic f each other stronger (C = competitor) ◊ Plants that occur under this kind of e water, light, and minerals ® Lower left corner is areas that experience and little competition ◊ Poor soils/deserts ◊ Grime argued that stress tolerant pla nutrient efficient, would use resource herbivores ® Lower right corner characterizes areas w ◊ No competition because the area is di

ngle d as low stress and low disturbance actors, they grow vigorously and compete with vironment will have superior abilities to acquire high levels of stress, but little disturbance

ts would grow slowly, would be evergreen to be slowly, and would taste bad to deter th high disturbance but low stress turbed and all plants are killed

◊ Grime called "rooterals:" short life sp § Where as the r-k model saw a continuum of life his extreme categories not two □ And the stress tolerators and the competitors selected traits § Continuumn of categories/trait mixtures rather th

□

○ Fast-slow plant economic spectrum § Some plants grow quickly and have short lives whe § Spectrum of plant tradeoffs

ns, rapid growth rate, produces lots of seeds tory traits, grime argued that there's three divide up what was previously thought to be kan discrete categories

eas others grow slowly and have long lives...