1. KEY CONCEPT Organisms interact as individuals and as populations.

2. Competition and predation are two important ways in which organisms interact.
Competition occurs when two organisms fight for the same limited resource.
Intraspecific competition
Interspecific competition

3. Predation occurs when one organism captures and eats another.

4. There are three major types of symbiotic relationships.
Mutualism: both organisms benefit

5. There are three major types of symbiotic relationships.
Commensalism: one organism benefits, the other is unharmed
Human Our eyelashes are home to tiny mites
that feast on oil secretions and dead skin. Without harming us, up to 20 mites may be living in one eyelash follicle.
Demodicids Eyelash mites find all they need to survive in the tiny follicles
of eyelashes. Magnified here 225 times, these creatures measure 0.4 mm in length and can be seen only with a microscope. +
Organism benefits Ø
Organism is not affected
Commensalism

6. There are three major types of symbiotic relationships.
Parasitism: one organism benefits, the other is harmed
Organism benefits _
Organism is not affected
Hornworm caterpillar
The host hornworm will eventually die as its organs are consumed
by wasp larvae.
Braconid wasp
Braconid larvae feed on their host and release themselves shortly before reaching
the pupae stage of development.
Parasitism +

7. There are three major types of symbiotic relationships.
Parasitism meet their needs as ectoparasites (such as leeches) and endopaasites (such as hookworms)

8. KEY CONCEPT Each population has a density, a dispersion, and a reproductive strategy.

9. Population density is the number of individuals that live in a defined area.
Population density is a measurement of the number of individuals living in a defined space.
Scientists can calculate population density.

10. Population dispersion refers to how a population is spread in an area.
Geographic dispersion of a population shows how individuals in a population are spaced.
Population dispersion refers to how a population is spread in an area.
Clumped
dispersion
Uniform
Random

11. There are three types of dispersion.
clumped

12. There are three types of dispersion.
uniform

13. There are three types of dispersion.
random

14. Survivorship curves help to describe the reproductive strategy of a species.
A survivorship curve is a diagram showing the number of surviving members over time from a measured set of births.

15. Survivorship curves can be type I, II or III.
Type I—low level of infant mortality and an older population
common to large mammals and humans
Type II—survivorship rate is equal at all stages of life
common to birds and reptiles
Type III—very high birth rate, very high infant mortality
common to invertebrates and plants

16. KEY CONCEPT Populations grow in predictable patterns.

17. Changes in a population’s size are determined by immigration, births, emigration, and deaths.
The size of a population is always changing.
Four factors affect the size of a population.
immigration
births
emigration
deaths

18. Population growth is based on available resources.
Exponential growth is a rapid population increase due to an abundance of resources.

19. Logistic growth is due to a population facing limited resources.

20. Carrying capacity is the maximum number of individuals in a population that the environment can support.
A population crash is a dramatic decline in the size of a population over a short period of time.

21. Ecological factors limit population growth.
A limiting factor is something that keeps the size of a population down.
Density-dependent limiting factors are affected by the number of individuals in a given area.

22. Density-dependent limiting factors are affected by the number of individuals in a given area.
predation
competition
parasitism and disease

23. Density-independent limiting factors limit a population’s growth regardless of the density.
unusual weather
natural disasters
human activities