Life History & Demography Flashcards
positive effects of asexual reproduciton
- higher fitness
- rapid population growth
negative effects of asexual reproduction
- low genetic variability
- no way to get rid of bad genes
porfolio effect
genetic diversity allows orgaisms to respond better to environmental conditions
hermaphroditic
organisms have male and female organs
life history
sequence of organim’s life events; way that they allocate resources for growth and survival
life history trade-off
between survival and fecundity
life history trait
heritable trait that determines an aspect of organism’s life history and can change with conditions (e.g. number of offspring, lifespan)
life history strategy
pattern of traits that evolved by natural selection
high fedundity-low survivorship
- reach sexual maturity earlier
- produce many eggs/seeds
high survivorship-low fecundity
- grows slowly
- traits that protect from predators
demography
study of factors that determine population size and structure
4 factors affecting demography
- birth
- death
- immigration
- emigration
life table
a table that includes:
- age
- number of individuals
- fecundity
- survivory ship
- number of offspring/female born (survivorship x fecundity)
survivorship
proportion of individuals remaining from one age class to the next
types of surivorship curves
type 1: high survivorship when young, low when old
type 2: steady
type 3: low survivorship when young, high when old
fecundity
number of female offsping produced
R0
the growth rate of a population per generation, stable if R0=1
survivorship curve of albertosaurus
predicted to be: type 3
actual: type 1
per-capita popualtion growrth rate (r)
r = b-d
- difference between birth rate and death rate
- if r = 0, steady growrth rate
How to calculate r based on R0?
r = ln(R0) / G
population growth equation
Nt = N0^(r x t)
maximum intrinsic growth rate (r max)
- when birth rates peak and death rates are as low as possible
- does not change for a species
exponential population growth
population growth = r (N)
- r remains constant
- growth is not based on population size
- can occur for new population or bottleneck
- does not consider competition
logistric population growth
population grorwth = (r) (K-N/K) (N)
- r declines
- growth is based on (declining) population size
- K = carrying capacity
density dependent
- based on growing/shrinking population size
- factors are biotic (food, predators)
density independent
- based on a constant population size/growth
- factors are abiotic (weather, natural disaster)
antagonistic selection
when components of fitness oppose each other (e.g. sexual vs. fecundity)
principle of allocation
enegry used for one function will reduce the enegry available for another
semelparous
individuals generate multiple offspring, providing little parental care; increases fitness of parent but decreases fitness of young
iteroparous
individuals produce less offspring with more parental care; increases fitness of young but decreases parent fitness
metapopulations
populaitions that are linked by immigration/emigration
ecological footprint
land and water area needed to sustain a population
extinct
all members of species are not found anymore
extinct in the wild
only living members of species are in captivity
locally extinct
members of species are no longer found in a specific area
ecologically extinct
members are reduced that it no longer has an effect on its community
overkill hypothesis
human hunting resulted in the megafaunal excitntion
background exctinction
the cause of most exctinctions
ecosystem services
processes where natural ecosystems benefit humans (air purification, nutrient cycles)
3 major causes of endangered spp
habitat loss, pollution, overexploitation
Which mass excintion are we currently in?
6th, human induced
