1. Species Interactions in an Ecosystem
Populations
and
Species Interactions in an Ecosystem

2. A habitat differs from a niche.
A habitat is all aspects of the area in which an organism lives. (location)
An ecological niche includes all of the factors that a species needs to survive, stay healthy, and reproduce. (Role in ecosystem)
food
Behavior 2

3. Competition occurs when two species use resources in the same way.
Competitive exclusion keeps two species from occupying the same niche. Competitive exclusion has different outcomes.
Resource availability gives structure to a community.
1) One species is better suited to the niche and the other will either be pushed out or become extinct.
2) The niche will be divided. The two species will further diverge. 3

4. Intraspecific competition (between SAME Species; Mates)
Competition and predation are two important ways in which organisms interact.
Competition occurs when two organisms fight for the same limited resource.
Intraspecific competition
(between SAME Species; Mates)
Interspecific competition
(between 2 Different Species; Food) 4

5. Predation occurs when one organism captures and eats another.5

6. There are three major types of symbiotic relationships.
1) Mutualism: both organisms benefit (+/+) 6

7. 2) 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 7

8. 3) Parasitism: one organism benefits, the other is harmed_
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 + 8

9. Parasitism meet their needs as ectoparasites (such as leeches) and endopaasites (such as hookworms)

10. Scientists can calculate population density.
Population density is the number of individuals that live in a defined area.
Scientists can calculate population density. 10

11. Population dispersion refers to how the individuals in a population are spread in an area.
Clumped
dispersion
Uniform
Random 11

12. Survivorship curves help to describe the reproductive strategy of a species & is a diagram showing the number of surviving members over time from a measured set of births. 12

13. Survivorship curves can be type I, II or III.
Type I —low level of infant mortality and an older population; large mammals and humans
Type II—survivorship rate is equal at all stages of life; birds and reptiles
Type III—very high birth rate, very high infant mortality; insects, fish and plants 13

14. Changes in a population’s size are determined by four factors: immigration, births, emigration, and deaths.
The size of a population is always changing. Population growth is based on available resources. 14

15. Exponential growth is a rapid population increase due to an abundance of resources. (J- shaped curve) 15

16. Logistic growth is due to a population facing limited resources
Logistic growth is due to a population facing limited resources. (S shaped curve)
Carrying capacity is the maximum number of individuals in a population that the environment can support; Limits pop. growth 16

17. 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. 17

18. Competition (food/shelter) parasitism
Density-dependent limiting factors are affected by the number of individuals in a given area.
Predation
Disease
Competition (food/shelter)
parasitism 18

19. Animation of limiting factors
Density-independent limiting factors limit a population’s growth regardless of the density.
unusual weather
natural disasters
human activities
Animation of limiting factors 19

20. Succession occurs following a disturbance in an ecosystem.
a sequence of biotic changes
damaged communities are regenerated
new communities arise in previously uninhabited areas

21. There are two types of ecological succession.
primary succession — started by pioneer species (lichens); bare rock- nothing living there before:

22. There are two types of succession.
secondary succession — started by remaining species; once living things; soil still intact