Interactions of Organisms in Ecosystems (Unit 3 – LT)

1. Interactions of Organisms in Ecosystems (Unit 3 – LT)

2. KEY CONCEPT Every organism has a habitat and a niche. A habitat differs from a niche.

3. Habitat • The area or environment where an organism or ecological community normally lives or occurs: Marine habitat

4. Niche >Rhymes with itch! The functional role of a species in its environment‚ includes: Food- how it fits in a food web Behavior-interaction with other organisms and environment Abiotic conditions it can tolerate. I think of my niche as my job! Clown fish living among the tentacles of a sea anemone.

5. KEY CONCEPT Organisms interact as individuals and as populations. Competition and predation are two important ways inwhich organisms interact.

6. Competition • Competition occurs when two organisms compete for thesame resource. • Intraspecific Competition involving the same species • Interspecific Competition • involving different species

7. Predation occurs when one organism captures and eat another.

8. Symbiotic Relationships or Symbiosis Symbiosis is a close ecological relationship between the individuals of two (or more) different species. There are three major types of symbiotic relationships.

9. Mutualism: • both organisms benefit . Bat eats nectar. Cactus is pollinated. + + + + Organism benefits + + + Organism benefits

10. Commensalism 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. Ø 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. + Ø + Organism is not affected Organism benefits Commensalism: • - one organism benefits, the other is unharmed

11. Braconid wasp Braconid larvae feed on their host and release themselves shortly before reaching the pupae stage of development. + Parasitism + _ Hornworm caterpillar The host hornworm will eventually die as its organs are consumed by wasp larvae. _ Organism benefits Organism is affected negatively + Parasitism: • one organism benefits, the other is harmed

12. Parasites meet their needs as either Ectoparasites-outside the body of host Endoparasites- inside the body of host Hookworm Leech

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

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

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

16. 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. Survivorship curves can be type I, II or III.

17. Type I • Low level of “infant” mortality • One to two offspring • An older population • Slow to reach reproductive age • Common to large mammals and humans Baboon

18. What ‘ll it be berries or worms? Feed us now! Type II • survivorship rate is equal at all stages of life • Multiple offspring • Reproductive age usually reached in one or two years • Common to birdsand reptiles

19. Type III • Very high birth rate • Very high infant mortality • Usually reach sexual maturity in one season • Common to invertebrates and plants Cicada

20. KEY CONCEPT Populations grow in predictable patterns.

21. The size of a population is always changing. . Four factors affect the size of a population. • Immigration (in) • Emigration (out) • Births • Deaths

22. Population Growth • Population are directly effected by the amount of resources available. • There are two distinct types of population growth

23. Exponential Growth • Exponential growth is a rapid population increase due to an abundance of resources. Australian farmer introduced 24 rabbits (European) in 1859 today there are ~ 300 million rabbits.

24. Logistic Growth • Logistic growth is due to a population facing limited resources. Starts slowly then becomes exponential growth but levels off as resources become scarce.

25. Carrying Capacity • Carrying capacity is the maximum number of individuals in a population that the environment can support.

26. Population Crash • A population crash is a rapiddecline in the size of a population over a short period of time. Carrying capacity

27. Ecological factors limit population growth. • A limiting factor is “something” that keeps the size of a population down. Density Dependent Density Independent

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

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