1. Chapter 8: Populations Population size, density & distribution

2. What is a population?
Group of organisms of the same species interacting in the same area
Also inter-breeding
In natural populations, individuals can be…
unitary = genetically unique
modular = genetic clones
Most animals are unitary while many plants, fungi, protists can be modular
Modular plants are interconnected stems or clumps

3. Stolon – horizontal stem (above ground) that extends out to create a new individual clump
Rhizome – root system that sprouts many individual clumps above ground

4. Examples of modular organisms
Mint
May-apple
Coral

5. Distribution Distribution = spatial location, area over which it lives
Influenced by habitat conditions & resource distribution

6. Distribution & geographic range
If a given distribution includes the entire species, it is called the geographic range
Ubiquitous = A species with a broad, widespread range made up of many populations
Endemic = range is narrow containing few populations

7. Various levels of the distribution of a moss species
Tetraphis pellucida

8. What is a meta-population?
A group of populations that are connected by individuals who move back and forth among them

9. Population size & density
Abundance = the total number of individuals in the population
Density = number of individuals per unit area (also known as crude density)

10. Population Density Crude Density can be misleading, why?
Not all individuals are uniformly distributed across the landscape
Can be clumped around resources
Can be randomly scattered by other forces
Ecological density = number of individuals per unit of suitable habitat

11. Ecological Density in Bobwhite

12. 3 patterns of spatial distribution

13. 3 patterns of spatial distribution

14. 3 patterns of spatial distribution

15. Determining Population Size
Quadrat Sampling
create a grid or squares on a landscape
count individuals in each square
multiply by number of squares on landscape
can be affected by distribution pattern

16. Quadrat Sampling
Results of quadrat sampling should always include a confidence factor based on distribution pattern

17. Determining Population Size
Mark & Recapture
capture and mark individuals
release marked individuals back into population
re-capture some and count marked individuals
use ratios tom determine population size

19. Determining Population Size
Indices of Abundance
locate signs, sounds, evidence of individuals
estimate number of individuals based on evidence
Examples: Frog calls, bird calls, animal tracks, scat, trail cameras, etc…

20. Determining Population Size
Which method should be used?
Quadrat – sessile (non-mobile) organisms
Mark & Recap. – mobile individuals
Indices – elusive individuals in small numbers

21. What is dispersal? Dispersal = movement of individuals in space
Immigration – individuals enter a population
Emigration – individuals leave a population
Immigration & Emigration = one-way trip
Migration is a round-trip that occurs at a regular time interval
Birds have an annual migration to warmer climate
Plankton have a daily migration between deep and shallow water

22. What is Age Structure?
Age Structure = the number or proportion of individuals in different age classes in a population
3 basic categories or age classes:
pre-reproductive
reproductive
post-reproductive
Age structure pyramid – graphical snapshot of the age structure of a population at some point in time

23. Age structure pyramids
What is happening in each of these populations?

24. Age structure pyramids - prediction
Shape of pyramid shows the growth pattern of the population:
Pyramid shape with a broad base and narrow top for expanding populations (positive growth)
Straight column with tapered top for stable populations (zero growth)
Straight column that is “top-heavy” for declining populations (negative growth)

25. Chapter 10 Stuff
K & r strategies

26. 2 reproductive strategies
Focus on one of the two main aspects of biotic potential:
birth rate or recruitment rate
Recruitment rate = % of offspring that reach reproductive age
Both strategies work
Not all organisms fit strictly into one category

27. r-selection Have tons of offspring but do not parent
All energy is put into mass producing offspring
Most young die, only one or two survive
Smaller animals
Useful for taking advantage of good conditions in a changing environment
Short life cycles
Insects, fish, etc…

28. K-selection
Have few offspring but raise a high % to reach adulthood – parenting
Put energy into raising young
Most young survive, 1 or 2 out of a small brood
Larger animals, high on food chain
Longer life cycles / life spans
Used by species that are highly adapted to cope with normal environmental changes
Mammals, birds, people

29. Figure 9-9 Page 196 Carrying capacity K K species; experience
K selection
Number of individuals
r species;
experience
r selection
Time