Unit II The Living World

1. Unit IIThe Living World

2. Ecology • The study of organisms and how they relate to their environment (habitat). • Habitat • Consist of biotic and abiotic factors. • Biotic • Living components of the ecosystem • plants, animals, microbes • Abiotic • Non-living components of the ecosystem • water, air, nutrients

3. Biotic Hierarchy • Organism • Any form of life. • Populations • Two or more of the same species within a given area (habitat). • Communities • Two or more populations within a given area. • Ecosystem • Biotic & abiotic factors • Biosphere • A closed system with no outside matter. • Divided into regions known as biomes.

4. Energy • Only flows one way through the earth. • Critical matter or nutrients are cycled to sustain life. • Sun is the ultimate source of energy.

5. Energy • As energy flows through each step of a food web, it becomes more unusable. • Energy is converted into unusable forms (i.e. heat). • Endothermic organisms are ecologically expensive. • Converted for an organisms’ own respiration, metabolism, digestion, & predation. • Parts of organisms do not provide calories. • bones, scales

6. Respiration • Rate of energy used at each level to maintain life. • Generally 90% of the available calories. • More levels = less energy available in a usable form at next higher level. • Shorter food chains are more efficient but lack diversity.

10. Gross Productivity • The rate of conversion of solar energy into chemical energy. • Gross productivity • Total amount of energy that plants capture and assimilate in a given period of time • Net Productivity • Plant growth per unit area per time (g/m2/yr) • Represents the rate at which organic material is actually incorporated into the plant tissue for growth

11. Variations in PP per Ecosystem

12. Evolution • Evolution • Works through a combination of 4 processes: • Mutation • random changes in structure or # of DNA molecules • Natural Selection • survival of the fittest • Gene Flow • movement of genes between populations • Genetic Drift • Changes in genetic composition of a population by chance

13. Speciation • What is speciation? • Formation of new species from an older species. • Speciation – Extinction = Biodiversity • Populations change due to adaptations, natural selection, and mutations.

14. Speciation • Species Adaptations • Morphological • Specialized physical structures for habitat • ducks have webbed feet • Physiological • Specialized functions within an organism • venom in spiders • Behavioral • Specialized behaviors • migration

15. Speciation Methods • Most common new species formation method occurs in two phases: • Geographic Isolation • Populations are separated by physical barriers for long periods into areas with different environmental condition. • Reproductive Isolation • Mutation and natural selection occur within the geographically isolated populations. • Combined process is known as divergent evolution.

16. Speciation Methods • Adaptive Radiation • New species evolve to fill new or vacated niches in changed environments. • Ex: Darwin’s finches • Coevolution • Adaptations based on dependence to another organism. • Formed symbiotic relationships • Ex: clownfish and anemones

17. Natural Selection • Directional Movement of an entire population to one extreme ex: giraffes 2. Divergent/Diversifying Adaptations from a common ancestor found in geographically isolated areas. ex: ostriches, rheas, emus 3. Stabilizing Movement of an entire population away from extremes ex: mice

18. Ecosystem Components • Population Diversity & Density • Diversity • Number of different populations in a community. • Density • The size in numbers of each population. • Niche • A species’ role in their ecosystem.

19. Producers and Consumers • Producers (Autotrophs) • Make their own food from compounds in their environments. • Bases of food webs. • Consumers (Heterotrophs) • Get food by ingesting other living organisms or their remains.

20. Consumers • Primary Consumers • Eat producers • Secondary Consumers • Eat 1º Consumers • Tertiary Consumers • Eat 2º Consumers • Omnivores • Eat both plants and animals • Scavengers • Eat organisms killed by other organisms or died naturally.

21. Consumers • Detritivores • Eat detritus • parts of dead organisms & waste of living organisms • Decomposers • Break down last remnants of organic material. • Return nutrients back to the environment.

23. Specialist Species • Definition • Organism in a narrow niche with no predators. • Advantages • Competition is reduced. • Disadvantages • When food and habitat are limited, survival is threatened due to lack of adaptability. • Example: • Koalas

24. Generalist Species • Definition • Organisms w/ a wide niche, usually no predators. • Advantages • Wide niche and habitat choices. • Disadvantages • Competition from other species. • Example: • Racoons

25. Other Species Classifications • Keystone Species • Definition • Species w/ a central role in the functioning of an ecosystem and the existence of other species are closely tied to them. • American Alligator • Indicator Species • Definition • Species that serve as an early warning that a community or ecosystem is being damaged. • Canaries & Most Amphibians

26. Limiting Factors • Law of Tolerance • Organisms have a limit to the range of minimum and maximum tolerance for change. • Conditions approaching or exceeding the limits of tolerance are called limiting factors. • Threshold • Point at which harmful or fatal reactions occur. • May be difficult to determine in advance. • Optimum Range • Where survival is best.

28. Competition • Survival of the Fittest • “Fittest” doesn’t usually mean strongest but species able to avoid competition as much as possible. • Interference • Limiting another organism’s access to resources. • Ex: establishing a territory • Exploitation • One organism is better at using a particular resource • Ex: lions are more adept at attacking larger prey than leopards • Competitive Exclusion • Similar organisms cannot occupy the same niche indefinitely. • Ex: alligators and crocodiles

29. Avoidance • Resource Partitioning • Organisms w/ similar resource requirements divide up scarce resource use at different times or different places. • Ex: birds dividing up a tree diurnal patterns of reef fish

30. Avoidance • Character Displacement • Similar organisms develop physical or behavioral features that allow them to use different resources. • Ex: Darwin’s finches

31. Symbiosis • Parasitism • One organism benefits while harming another (+/-) • Ex: Lamprey on fish • Mutualism • Both organisms benefit (+/+) • Ex: Mycorrihzal fungi and plant roots • Commensalisms • One organism benefits while the other is not affected (+/0) • Ex: epiphytes in a tropical tree

32. Predation • Importance • Harmful to individual prey but necessary at population level. • Keeps population in check • Weeds out sick and injured • Predator-Prey Relationship • Relationship between a predator species and its prey.

33. Predation • Enhancements • Speed • Keen Eyesight, sense of smell • Hunting in packs • Ambush • Flight • Chemical Attack/Defense • Camouflage

34. Succession • Definition • Way all ecosystems age in a (theoretically) predictable way. • However nature is unpredictable. • Primary Succession • Begins with an essentially lifeless area. • Terrestrial – no soil • Aquatic – no bottom sediment • Typical Progression Lichen mosses grasses shrubs forests

35. Secondary Succession • Where does it occur? • Occurs in area where the habitat has been disturbed, removed, or destroyed. • Soil is still intact though

36. Stability • Based on 3 parameters • Inertia • Resistance to change • Constancy • Ability of a population to live within the available resources • Resilience • Ability of an ecosystem to recover