1. 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.

2. Fields of Ecology Organismal Ecology (physiology, behavior)
Population Ecology (life history strategies, demography, population growth)
Community Ecology (species interactions, biodiversity)
Ecosystem Ecology (energy & nutrient flow, landscape ecology)

3. 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.

4. Life History Characteristics
Growth
Change of form
Dispersal
Timing of reproduction
Size at birth or germination
Number and size of offspring
Age at death

5. 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.

6. Life History – Change of Form
Change of form - many organisms have dramatically different forms or stages in their life cycle.

7. Life History - Dispersal
At some time in their lives, most organisms go through dispersal – enhances reproductive success.
Belding’s Ground Squirrel
Spiders
Milkweed

8. Life History Characteristics
Growth
Change of form
Dispersal
Timing of reproduction
Size at birth or germination
Number and size of offspring
Age at death

9. LIFE HISTORY STRATEGIES (LHSs):
Patterns of lifespan and reproduction
that characterize a species.
LHSs are a result of natural selection,
which acts on individuals, NOT species

10. Individuals that have a life history that
maximizes fitness will be favored by
natural selection…
…thus, particular patterns of survival
and reproduction will eventually be
shared by all members of a population.

11. Three Main Life History Strategies:
Survivorship
Maturity
Reproductive Output

12. 3) Reproductive Output
Parity
# reproductive episodes in lifetime

13. Semelparous species Salmon Mayfly Agave
Mayflies in order Ephemeroptera (“ephemeral”) – live only 24 hrs, do not even feed
Agave
Semelparous species

14. Iteroparous Species

15. 3) Reproductive Output
Parity
Fecundity
# offspring per reproductive episode

16. elephants
rodents
spiders

17. 3) Reproductive Output
Parity
Fecundity
Parental Investment
Energetic effort put into offspring:
Size of offspring

18. 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.

19. Number of Offspring Offspring Size
General Relationship between Offspring Size
and Number of Offspring
Many
Number of
Offspring
Few
Small Large
Offspring Size

20. 3) Reproductive Output
Parity
Fecundity
Parental Investment
Energetic effort put into offspring:
Size of offspring
Parental care

21. LHS of a hypothetical “super-organism”?

22. Real LHSs are compromises in the
allocation of energy!
Reproductive Trade-offs:
Reproduction vs Future Survival

23. Reproduction vs Survival (Mortality)

24. How does caring for offspring affect parental survival in kestrels?
100
Male
Female 80 60
Parents surviving the following winter (%) 40 20
Reduced
brood size
Normal
brood size
Enlarged
brood size
Fig. 53-8

25. Reproductive Trade-offs:
Reproduction vs Future Survival
Reproduction vs Future Growth
Current vs Future Reproduction

26. Annual Meadowgrass Current vs Future Reproduction vs Future
Growth

27. Particular combinations of LHSs often favored in particular body sizes…
…but there are always exceptions to the rule!

28. Big Brown Bat (Eptesicus fuscus)
Baby bat
Longer lifespan (14 yrs) and lower fecundity (1-2)
than expected for a mammal of that size (small)

29. A few, large offspring.
Parental care in carrion beetles;
very unusual for an insect.

30. “Octomom”

31. LHSs characterize species, but can also be somewhat flexible – different populations can adapt to different environmental conditions…

32. e.g. Fat-tailed Dwarf Lemur
Pop 1: dry forest,
long torpor (6-7 months):
Fewer, smaller litters.
Pop 2: rainforest,
shorter torpor (4-5 months) and higher mortality rates:
More frequent, larger litters.

33. Trade off between longevity and number of offspring:
Long life span selects for low reproductive investment.
Short life span selects for high reproductive investment

34. DEMOGRAPHY
The study of birth and death processes
that determine growth and age structure
of a population.

35. Each age class of a population has an expected:
Mortality rate
Fecundity rate

36. Demographic characteristics can be represented in:
Life Tables
summarize deaths and/or births
in different age classes of a population
Conventional life table

38. Demographic characteristics can be represented in:
Life Tables
summarize deaths and/or births
in different age classes of a population
Conventional life table
Diagrammatic life table (flow diagram)

39. 2) Survivorship Curves Fig. 53-6 Number of survivors (log scale) 1,000
100 II
Number of survivors (log scale) 10
Figure 53.6 Idealized survivorship curves: Types I, II, and III
III 1 50
100
Percentage of maximum life span
Fig. 53-6