What is Ecology?
Scientific study of the interactions of organisms with their abiotic and biotic environments...
...in order to understand the distribution and abundance of organisms in space and time.
Fields of Ecology
Organismal Ecology (morphology, physiology, behavior)
Population Ecology (life history strategies, demography, population growth)
Community Ecology (species interactions, biodiversity)
Ecosystem Ecology (energy & nutrient flow, landscape ecology)
Population Ecology• A population is a group of individuals of the same
species that live in a particular area and have the potential to interbreed.
Flock of Starlings at Dusk – U.K.
Population ecologists are primarily interested in
a) understanding how biotic and abiotic factors influence the density, distribution, size, and age structure of populations.
b) the overall vitality of a population of organisms.
c) how humans affect the size of wild populations of organisms.
d) studying interactions among populations of organisms that inhabit the same area.
e) how populations evolve as natural selection acts on heritable variations among individuals and changes in gene frequency.
Life History Characteristics:
• Growth
• Change of form
• Dispersal
• Timing of reproduction
• Size at birth or germination
• Number and size of offspring
• Age at death
Life History - Growth
• Growth – for at least part of their life history, all organisms grow by assimilating energy and nutrients – final body size species-specific.
Life History – Change of Form• Change of form - many organisms have
dramatically different forms or stages in their life cycle.
Life History - Dispersal
• At some time in their lives, most organisms go through dispersal – enhances reproductive success.
Belding’s Ground Squirrel Spiders Milkweed
Life History Characteristics
• Growth
• Change of form
• Dispersal
• Timing of reproduction
• Size at birth or germination
• Number and size of offspring
• Age at death
LIFE HISTORY STRATEGIES (LHSs):
Patterns of lifespan and reproductionthat characterize a species.
LHSs are a result of natural selection, which acts on individuals, NOT species
…thus, particular patterns of survival and reproduction will eventually beshared by all members of a population.
Individuals that have a life history thatmaximizes fitness will be favored bynatural selection…
Three Main Life History Strategies:
1) Survivorship
2) Maturity
3) Reproductive Output
3) Reproductive Output
a) Parity
# reproductive episodes in lifetime
Agave
Salmon
Semelparous species
Mayfly
Iteroparous Species
Your textbook says, “The fundamental idea that evolution accounts for the diversity of life is manifest in a broad range of life histories found in nature.” Based on what you know about evolution by natural selection, you can predict that species that have evolved semelparity have done so because:
A) semelparous parents produce more offspring if they invest all of their resources in reproduction than they would if they saved enough resources to survive until they can reproduce again.
B) semelparous parents produce offspring that are more likely to survive than offspring produced by iteroparous parents.
C) iteroparous parents are less likely to provide parental care than semelparous parents.
D) semelparous parents and iteroparous parents are equally likely to produce offspring; semelparity evolved for other reasons.
E) iteroparous parents are more likely to die before they can reproduce than are semelparous parents.
Two factors influence evolution of semelparity vs iteroparity:
• Survival probability of offspring
• Probability that adults will survive to reproduce again
Both probabilities are low in harsh or unpredictable environments, so semelparity will be favored.
3) Reproductive Output
a) Parity
b) Fecundity
# offspring per reproductive episode
elephants
rodents
spiders
3) Reproductive Output
a) Parity
b) Fecundity
c) Parental Investment
Energetic effort put into offspring:
i) Size of offspring
• Some plants produce a large number of small seeds, ensuring that at least some of them will grow and eventually reproduce.
• Other types of plants produce fewer large seeds that provide a large store of energy that will help seedlings become established.
Offspring Size
Small Large
Numberof
Offspring
Many
Few
General Relationship between Offspring Sizeand Number of Offspring
3) Reproductive Output
a) Parity
b) Fecundity
c) Parental Investment
Energetic effort put into offspring:
i) Size of offspring
ii) Parental care
LHS of a hypothetical “super-organism”?
Real LHSs are compromises in theallocation of energy!
Reproductive “Trade-offs”:
a) Reproduction vs Future Survival
Reproduction vs Survival (Mortality)
Fig. 53-13
MaleFemale
100
80
60
40
20
0Reduced
brood sizeNormal
brood sizeEnlargedbrood size
Par
ents
su
rviv
ing
the
foll
owin
g w
inte
r (%
)
How does caring for offspring affect parental survival in kestrels?
In some bird species, the male provides no care. If this were true for the European Kestrel, how would the experimental results differ?
A) Females in all three groups likely would have the same survival values as in the graph.
B) Males in all three groups likely would have higher survival % than females.
C) Patterns for both males and females likely would remain the same.
D) Only females with reduced brood sizes likely would show a reduced survival.
Reproductive Trade-offs:
a) Reproduction vs Future Survival
a) Reproduction vs Future Growth
b) Current vs Future Reproduction
Reproduction vs FutureGrowth
Current vs Future Reproduction
Annual Meadowgrass
Particular combinations of LHSs often favored in particular body sizes…
…but there are always exceptions to the rule!
Baby batBig Brown Bat (Eptesicus fuscus)
Longer lifespan (14 yrs) and lower fecundity (1-2) than expected for a mammal of that size (small)
Parental care in carrion beetles;very unusual for an insect.
A few, large offspring.
“Octomom”
