topic 10 - reproduction Flashcards
what is the ideal environment
unlimited resources to support maximal growth, long life, and continuous production of offspring (with high survival)
what is the ultimate goal of managing an energy budget properly
to have energy remaining to allocate to reproduction
what is the life history theory
every species has a pattern of growth and development, reproduction, and death shaped by natural selection
how does maximised reproductive success occur
tradeoffs due to fixed energy budgets (can’t maximise everything) and selective pressures
- environment (the way that the environment shapes the species and its performance - ability to turn energy into offspring)
what is abiotic and biotic
abiotic = weather
biotic = organisms that live nearby
what is a tradeoff
if 2 life history traits compete for a share of limited resources, then it’s impossible to maximise both traits simultaneously
- any gains in one trait will result in a loss by the other
what does a positive relationship mean in terms of tradeoff
no tradeoff
both traits can increase at no expense of the other
what does a negative relationship mean in terms of tradeoff
tradeoff between the traits
one can increase at the expense of the other
what is indeterminate growth
growth of the organisms continues throughout the lifespan
ectotherms - reptiles, fish, plants, etc
what is determinate growth
growth of the organism ceases when “adult” state is reached
endotherms - birds, mammals, etc
(some plants grow to a certain size and then push all energy into reproduction)
what is asexual reproduction
produces clones
prokaryotes replicate genome and divide by binary fission
some eukaryotes replicate their genome and divide through mitosis
doesn’t involve wasted energy
what is sexual reproduction
produces recombinants
only in eukaryotes
merging of different lineage (very different evolutionary processes)
energetic and evolutionary cost
what are life history traits
Growth rate
Parental investment
Number of offspring (fecundity)
Frequency of reproduction (parity)
Size / age at sexual maturity
Size of offspring
Longevity / life expectancy (mortality rate)
all traits can evolve and there is genetic variation in all traits
what is the tradeoff between growth and reproduction
high growth rate = less energy left over for reproduction
low growth rate = high energy left for reproduction (higher reproductive rate)
variation within species - due to genetic or environmental differences
what is the difference between pre and post birth energy investment
pre birth energy investment = seed development, gestation, etc (passive care)
post birth energy investment = raising offspring - investing in care after birth (active care)
(plants are not capable of active care)
what is the relationship between parental investment and number of offspring
high investment = less offspring (high survival)
less investment = more offspring (less survival)
what is the tradeoff between reproduction and survival of parent
survival decreases as reproduction increases
what is parity
how often an individual reproduces
what is semelparity vs iteroparity
semelparity
- individuals of the same species can breed only once in its lifetime
- breed and die
iteroparity
- Individuals of the same species can breed more than once in its lifetime
- breed and then continue to life
- ancestral - most life forms are iteroparous - where life evolved from
what is fecundity
ability to make many offspring
what is the relationship between fecundity and body size
increases with body size
larger = more eggs (not a tradeoff)
advantage to delaying sexual maturity until larger
what is the tradeoff between mating and lifespan
mated females = shorter lifespan (fruit flies)
energetic cost on eggs (less energy left over for disease protection, etc)
how does predation influence life history traits
fewer predators = larger size at reproduction
more predators = smaller size at reproduction
higher predation = smaller size at maturity (spending more energy escaping with less energy left over to invest in growth)
what are the life history strategies of r-selected species
Small offspring / adult size
Early sexual maturity
Often semelparous
High fecundity (lots of offspring)
Little parental investment
Low juvenile survivorship
Short lifespan
Evolved to reproduce quickly
associated with high population changes (booms and busts)
what are the life history strategies of k-selected species
Large offspring / adult size
Late sexual maturity
Iteroparity
Low fecundity (not many offspring but invest a lot into the ones they do make - high survival expected)
High parental investment
High juvenile survivorship
Long lifespan
Evolved to compete
why are life history tables useful
managing crops and livestock (farming planning)
conservation efforts (captive breeding programs)
pest/weed control
what is the rate limiting step in population growth
females
what do numbers at x=0 mean
characteristics of all individuals that are 0 years old
what does lx mean
fraction of original cohort that is still allive (l = living)
lx = nx/no
(no = number of individuals at time 0)
(nx = number of individuals at
always trending down
what is sx
survival from one age class to the next
sx = (nx+1)/nx
(nx =numbers of individuals at chosen year)
(nx+1 = number of individuals still alive in year after)
can go up and down in theory
what is Ro
net reproductive rate
Ro = sum(lx*mx)
what do Ro values indicate
Ro >1.01 = population increasing
Ro < 0.99 = population decreasing
0.99 < Ro < 1.01 = considered relatively
what are the axes on a survivorship curve
x = % of max lifespan the animal made it to
y = log scale
what is a type 1 survivorship curve
Low mortality until end of life
Large animals
Few young
High parental care
High juvenile survivorship
K selected
plateau and then drop off
what is a type 2 survivorship curve
Constant rate of mortality throughout the lifespan
Change of death is constant throughout life - could be due to high predation
Mix of r and K selected traits
what is a type 3 survivorship curve
Low juvenile survivorship
Mortality rate decreases with age - individuals that manage to survive young ages, live a long time
R selected
exponential decrease then plateau
how to find the shape of the survivorship curve
plot nx value from life history table
how to detect constant mortality
looks like type 3 on linear scale
looks like a straight line on log scale
