MODULE 4 OVERVIEW Flashcards
Define population
a group of individuals of the same species living in the same location
Features of a population
- rely on same resources
- influenced by same environmental conditions
- interact w/ each other & breed
What are the types of boundaries for a population?
- natural (lake, island, gut)
- arbitrary (natural park)
- need to be appropriate to the organism under study & to the questions
What are some properties of a population?
- size
- boundary
- distribution
- structure (sex ratio, age structure)
What is size affected by (how is it dynamic)?
- birth
- death
- immigration
- emigration
Distribution patterns depend on. . .
the SCALE at which we are looking
- clumped
- uniform
- random
Define population ecology
the scientific study of populations in relation to their environment and how biotic & abiotic factors influence the ABUNDANCE, DISPERSION & COMPOSITION of populations
What are 3 applications of population ecology?
- threatened species management
- pest control
- harvested populations
How do we estimate population size?
1) counting
2) sampling
What does precision in quadrat sampling depend on?
the NUMBER of plots
VARIABILITY in counts
What are the main types of marks in mark-recapture?
- artificial or natural
- genetic methods (feces / hair)
What are the 3 assumptions of mark-recapture?
1) marks are NOT lost b/w sampling sessions
2) marking does not alter the behaviour of individuals (trap-shy vs trap-happy)
3) closed population (no deaths, births, etc.)
violation of assumptions will lead to BIAS
Lengths of generations
- several generations per year
- one generation per year (annual)
- one generation over several years (perennial)
What is an iteroparous species?
individuals breed multiple times
resources during breeding dedicated to FUTURE survival
What is semelparous species?
single reproductive event
no resources dedicated to future survival; reproduction followed quickly by DEATH
What is demography?
the study of the vital statistics of populations & how they CHANGE over time
- can make a life table to summarize this info
What is stochasticity?
RANDOMNESS
A process if stochastic if. . .
it cannot be predicted accurately e.g. rolling a dice
Features of a deterministic process
NO RANDOMNESS INVOLVED
- outcome is certain
- exponential vs logistic model
What is one possible source of variation in animal populations?
- environmental stochasticity
- unpredictable fluctuations in env. conditions in SPACE + TIME
Demographic stochasticity becomes more important as. . .
population size declines
the average is very close to a DETERMINISTIC projection
Define migration
the seasonal movement of animals from one habitat to another in search of food, better conditions, or reproductive needs
dispersal
the movement from one breeding location to another (often influenced by age + sex)
What is natal dispersal?
from place of birth to 1st breeding place
What is breeding dispersal?
change of place of breeding
Modes of dispersal
- animals (active, passive) - fly, walk, currents, floods
- plants –> gravity, wind, water, animal
Dispersal has a fundamental influence on population dynamics. How?
1) invasive species
2) dynamics of metapopulations (contribute to local extinction, colonisation)
How is dispersal measured?
1) marking + observation
2) tracking technologies
3) intrinsic markers
What are some trade-offs to consider when trying to measure dispersal?
a) impact on animals (handling + device)
b) accuracy of info
c) size of the device, its price, its data collection capacity
Types of metapopulations
1) classic
2) mainland-island (source-sink)
3) non-equilibrium
4) patchy populations
5) mixtures
What is a life history?
pattern of survival and reproductive events for a species
Why do life histories look so different b/w species?
- life history patterns are an ‘optimization’ of tradeoffs b/w growth, survival, and reproduction
What are some factors to consider when studying reproductive behaviour?
- fecundity
- age of maturity
- single vs multiple reproductive events
What is fecundity?
an organism’s reproductive capacity
Female parents w larger brood =
lower survival rates
Pros of reproducing early
less risk of producing NO offspring at all
Cons of reproducing early
may be at expense of their health + growth
using all energy to reproduce to less energy used to grow
makes them more susceptible to predators
Pros of reproducing late
better fecundity + better able to care for their young
Cons of reproducing late
run the risk of not surviving to reproductive age
K selected =
density dependent
Logistic growth
r selected =
density independent
Exponential growth
What are features of K-selected species?
1) low rates of fecundity
2) high levels of parental investment in young
3) low rates of mortality of mature individuals
What are features of r-selected species?
1) high rates of fecundity
2) short gestation
3) low levels of parental investment in young
What is a parasite?
an organism that obtains its nutrients from a host or very few hosts, normally causing harm to the host but not necessarily causing death
Define vector
an organism that carries and transmits an infectious pathogen into another organism
Most parasites only have ___ host
ONE, or a limited number
‘host-specificty’
What are features of microparasites?
- small & often intracellular
- multiply directly within their host
- often extremely numerous
What are features of macroparasites?
- grow on / in but do not multiply their host
- produce infectious stages which they release into the env to find new hosts
- often live on the body or in body cavities instead of being INTRAcellular
How are parasites transmitted?
1) DIRECT (no vectors)
2) TROPHICALLY TRANSMITTED (eaten)
3) VECTOR TRANSMISSION
What are parasitic castrators?
reduce or remove their host’s reproductive ability & use the energy that would have gone into host production for parasite growth
host survives to sustain parasite
What are micropredators?
attack several hosts, usually feed on blood
e.g. leeches and vampire bats
What are parasitoids?
insects which eventually kill their hosts
Parasitoids - 2 methods
1) sting their large prey, carry it to a nest & lay an egg on top which hatches and feeds on the prey
2) lay their eggs directly into the host - the eggs hatch and grow in the living host, eventually emerging from the host
What kinds of strategies do parasites have?
Parasitic castrators
Micro-predators
Parasitoids
Brood parasites
Brood parasites
use another species to raise their young (insects, cuckoos)
To what extent are animal & plant populations affected by parasitism and disease?
1) pathogen virulence
2) whether the pathogen reduces host survival (death rate), reproduction (birth rate), or both
Microparasites drive . . .
really abrupt & severe changes in populations
What are epidemic diseases?
characterized by rapid changes in the prevalence of infection
when outbreaks occur, these pathogens cause waves of infection that can cause rapid population declines
What are endemic infections?
persist for long times in populations, showing relatively little fluctuation in prevalence
Epidemics can cause . . .
mass mortalities
What happened after the black death?
increased resources available for those that survived
population great at a greater rater AFTER than BEFORE
Micro- and macro-parasites that don’t kill their prey can affect (EPIDEMIC parasites can suppress populations)
1) birth rates
2) death rates, via increased predation
3) movement (immigration, emigration)
What are the 2 ways that hosts evolve?
- host tolerance
- host resistance
What is host resistance?
the ability of a host to reduce the probability that it is infected, reduce pathogen replication within the host, and / or increase the speed of pathogen clearance (recovery)
What is host tolerance?
the ability of a host to tolerate infection with a pathogen by minimizing the damage done but without impeding replication or transmission of the pathogen
What is the virulence-transmission trade-off hypothesis?
virulence is an unavoidable and increasing cost bc the parasite uses host resources to replicate
transmission is highest when
virulence is intermediate
Strategies for disease prevention & control of microparasites
culling –> used when transmission is thought to be density dependent
reduction of a wild animal population by selective slaughter.
Behavioural modifications including quarantine & social distancing
Vaccination – herd immunity
