Ecology

1. Ecology The study of interactions between organisms and their environment What role do bacteria play in ecology?

2. What does ecology examine? • Where do the organisms live? • Why do they live there? • How many are there?

3. Fig. 52-2 Organismal ecology Population ecology Community ecology Ecosystem ecology Landscape ecology Global ecology

4. Events that occur in ecological time affect life on the scale of evolutionary time • Ecologists consider multiple factors when attempting to explain the distribution of species

5. Fig. 52-6 Why is species X absent from an area? Yes Area inaccessible or insufficient time Yes Habitat selection Does dispersal limit its distribution? Yes Predation, parasitism, competition, disease Chemical factors Does behavior limit its distribution? No Do biotic factors (other species) limit its distribution? Water Oxygen Salinity pH Soil nutrients, etc. No Do abiotic factors limit its distribution? No Temperature Light Soil structure Fire Moisture, etc. Physical factors

6. Biotic Factors • Biotic factors that affect the distribution of organisms may include: • Interactions with other species • Predation • Competition

7. Abiotic Factors • Abiotic factors affecting distribution of organisms include: • Temperature • Water • Sunlight • Wind • Rocks and soil • Most abiotic factors vary in space and time

8. Fig. 52-10a Latitudinal Variation in Sunlight Intensity 90ºN (North Pole) 60ºN Low angle of incoming sunlight 30ºN 23.5ºN (Tropic of Cancer) Sun directly overhead at equinoxes 0º (equator) 23.5ºS (Tropic of Capricorn) 30ºS Low angle of incoming sunlight 60ºS 90ºS (South Pole) Atmosphere Seasonal Variation in Sunlight Intensity 60ºN 30ºN March equinox 0º (equator) June solstice 30ºS December solstice Constant tilt of 23.5º September equinox

9. Aquatic biomes are diverse and dynamic systems that cover most of Earth • Biomes are the major ecological associations that occupy broad geographic regions of land or water • Varying combinations of biotic and abiotic factors determine the nature of biomes

10. Stratification of Aquatic Biomes • Many aquatic biomes are stratified into zones or layers defined by light penetration, temperature, and depth

11. Fig. 52-16 Intertidal zone Oceanic zone Neritic zone Littoral zone Limnetic zone 0 Photic zone 200 m Continental shelf Pelagic zone Benthic zone Aphotic zone Photic zone Pelagic zone Benthic zone Aphotic zone 2,000–6,000 m Abyssal zone (a) Zonation in a lake (b) Marine zonation

12. Fig. 52-17-5 Summer Winter Spring Autumn 22º 4º 0º 4º 20º 4º 2º 4º 18º 4º 4º 4º 8º 4º 4º 4º 6º 4º 4º 4º 5º 4ºC 4ºC 4ºC 4ºC Thermocline

13. The structure and distribution of terrestrial biomes are controlled by climate and disturbance • Climate is very important in determining why terrestrial biomes are found in certain areas • Biome patterns can be modified by disturbance such as a storm, fire, or human activity

14. Fig. 52-19 Tropical forest Savanna Desert Chaparral 30ºN Temperate grassland Tropic of Cancer Equator Temperate broadleaf forest Tropic of Capricorn Northern coniferous forest 30ºS Tundra High mountains Polar ice

15. Community Ecology What niche do bacteria populations occupy in communities?

16. Overview: A Sense of Community • A biological community is an assemblage of populations of various species living close enough for potential interaction

17. Community interactions are classified by whether they help, harm, or have no effect on the species involved • Ecologists call relationships between species in a community interspecific interactions • Examples are competition, predation, herbivory, and symbiosis (parasitism, mutualism, and commensalism) • Interspecific interactions can affect the survival and reproduction of each species, and the effects can be summarized as positive (+), negative (–), or no effect (0)

18. Fig. 54-UN2

19. Ecological Niches • The total of a species’ use of biotic and abiotic resources is called the species’ ecological niche • An ecological niche can also be thought of as an organism’s ecological role • Ecologically similar species can coexist in a community if there are one or more significant differences in their niches

20. Fig. 54-2 A. distichus perches on fence posts and other sunny surfaces. A. insolitus usually perches on shady branches. A. ricordii A. insolitus A. aliniger A. christophei A. distichus A. cybotes A. etheridgei

21. Fig. 54-5 (a) Cryptic coloration Canyon tree frog (b) Aposematic coloration Poison dart frog (c) Batesian mimicry: A harmless species mimics a harmful one. Hawkmoth larva (d) Müllerian mimicry: Two unpalatable species mimic each other. Cuckoo bee Green parrot snake Yellow jacket

22. Fig. 54-8

23. Dominant and keystone species exert strong controls on community structure • In general, a few species in a community exert strong control on that community’s structure • Two fundamental features of community structure are species diversity and feeding relationships

24. Species Diversity • Species diversity of a community is the variety of organisms that make up the community • It has two components: species richness and relative abundance • Species richness is the total number of different species in the community • Relative abundance is the proportion each species represents of the total individuals in the community

25. Fig. 54-9 A B C D Community 1 Community 2 A: 80% B: 5% C: 5% D: 10% A: 25% B: 25% C: 25% D: 25%

26. Trophic Structure • Trophic structure is the feeding relationships between organisms in a community • It is a key factor in community dynamics • Food chains link trophic levels from producers to top carnivores • Food Web is a branching food chain with complex trophic interactions Video: Shark Eating a Seal

27. Fig. 54-11 Quaternary consumers Carnivore Carnivore Tertiary consumers Carnivore Carnivore Secondary consumers Carnivore Carnivore Primary consumers Herbivore Zooplankton Primary producers Plant Phytoplankton A terrestrial food chain A marine food chain

28. Fig. 54-12 Humans Smaller toothed whales Sperm whales Baleen whales Elephant seals Leopard seals Crab-eater seals Squids Fishes Birds Carnivorous plankton Euphausids (krill) Copepods Phyto- plankton

29. Characterizing Disturbance • A disturbance is an event that changes a community, removes organisms from it, and alters resource availability • Fire is a significant disturbance in most terrestrial ecosystems • It is often a necessity in some communities

30. Fig. 54-21 (a) Soon after fire (b) One year after fire

31. Ecological Succession • Ecological succession is the sequence of community and ecosystem changes after a disturbance • Primary succession occurs where no soil exists when succession begins • Secondary succession begins in an area where soil remains after a disturbance

32. Fig. 54-22-4 1941 1907 2 Dryas stage Pioneer stage, with fireweed dominant 1 0 5 10 15 Kilometers 1860 Glacier Bay Alaska 1760 4 Spruce stage 3 Alder stage

33. Human Disturbance • Humans have the greatest impact on biological communities worldwide • Human disturbance to communities usually reduces species diversity • Humans also prevent some naturally occurring disturbances, which can be important to community structure

34. Community ecology is useful for understanding pathogen life cycles and controlling human disease • Ecological communities are universally affected by pathogens, which include disease-causing microorganisms, viruses, viroids, and prions • Pathogens can alter community structure quickly and extensively

35. Fig. 54-29

36. Ecosystems An ecosystem consists of all the organisms living in a community, as well as the abiotic factors with which they interact How do bacteria contribute to balance in an ecosystem?

37. Conservation of Energy • Laws of physics and chemistry apply to ecosystems, particularly energy flow • The first law of thermodynamics states that energy cannot be created or destroyed, only transformed • Energy enters an ecosystem as solar radiation, is conserved, and is lost from organisms as heat • The second law of thermodynamics states that every exchange of energy increases the entropy of the universe • In an ecosystem, energy conversions are not completely efficient, and some energy is always lost as heat

38. Conservation of Mass • The law of conservation of mass states that matter cannot be created or destroyed • Chemical elements are continually recycled within ecosystems • Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products

39. Energy, Mass, and Trophic Levels • Autotrophs build molecules themselves using photosynthesis or chemosynthesis as an energy source; heterotrophs depend on the biosynthetic output of other organisms • Energy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) to secondary consumers (carnivores) to tertiary consumers (carnivores that feed on other carnivores)

40. Detritivores,or decomposers, are consumers that derive their energy from detritus, nonliving organic matter • Prokaryotes and fungi are important detritivores • Decomposition connects all trophic levels

41. Fig. 55-4 Tertiary consumers Microorganisms and other detritivores Secondary consumers Primary consumers Detritus Primary producers Heat Key Chemical cycling Sun Energy flow

42. What factors might influence primary production?

43. Energy and other limiting factors control primary production in ecosystems • Primary production in an ecosystem is the amount of light energy converted to chemical energy by autotrophs during a given time period • The extent of photosynthetic production sets the spending limit for an ecosystem’s energy budget

44. Gross and Net Primary Production • Total primary production is known as the ecosystem’s gross primary production (GPP) • Net primary production (NPP) is GPP minus energy used by primary producers for respiration • Only NPP is available to consumers • Ecosystems vary greatly in NPP and contribution to the total NPP on Earth • Standing crop is the total biomass of photosynthetic autotrophs at a given time

45. Fig. 55-6 · Net primary production (kg carbon/m2·yr) 0 1 3 2

46. Nutrient Limitation • More than light, nutrients limit primary production in geographic regions of the ocean and in lakes • A limiting nutrient is the element that must be added for production to increase in an area • Nitrogen and phosphorous are typically the nutrients that most often limit marine production

47. The addition of large amounts of nutrients to lakes has a wide range of ecological impacts • In some areas, sewage runoff has caused eutrophication of lakes, which can lead to loss of most fish species Video: Cyanobacteria (Oscillatoria)

48. Primary Production in Terrestrial Ecosystems • In terrestrial ecosystems, temperature and moisture affect primary production on a large scale • Actual evapotranspiration can represent the contrast between wet and dry climates • Actual evapotranspiration is the water annually transpired by plants and evaporated from a landscape • It is related to net primary production

49. Energy transfer between trophic levels is typically only 10% efficient • Secondary production of an ecosystem is the amount of chemical energy in food converted to new biomass during a given period of time

50. Fig. 55-9 Plant material eaten by caterpillar 200 J 67 J Cellular respiration 100 J Feces 33 J Growth (new biomass)