The hierarchy of life

1. The hierarchy of life

2. Species • Species: the different kinds of living things in a community • All individuals are like one another, but are distinct from other groups • Species are grouped into ________Which are grouped into families, orders, classes, phyla, kingdoms, and domains • The official species name is Latin and has two parts:

3. It is hard to define a species • All members that can interbreed and produce fertile offspring • Members of different species generally do not breed • This definition does not work for organisms that do not mate to produce offspring • Scientists use other classification methods • New species arise due to evolution • Species classifications are changed to reflect this

4. Populations and biotic communities • Population: a number of individuals that make up the interbreeding, reproducing group • It refers only to individuals of a species in an area • For example, gray wolves in Yellowstone National Park • A species would be all gray wolves in the world • A biotic community (biota): the grouping of populations in a natural area • Includes all vegetation, animals, and microscopic organisms

5. Species within a biotic community • The biotic community is determined by abiotic (nonliving chemical and physical) factors • Water, climate, salinity, soil • A community is usually named for its plants • Vegetation strongly indicates environmental conditions • Species in a community depend on each other • The plant community supports the animals • Populations of different species within a biotic community constantly interact • With each other and with the abiotic environment

6. Pine Forest Community

7. Ecosystems • Ecosystem: an interactive complex of biota and the abiotic environment within an area • A forest, grassland, wetland, coral reef • Humans are part of ecosystems • Ecosystems lack distinct boundaries and are not isolated • Species can occupy multiple ecosystems and migrate between them • Ecotone: a transitional region between ecosystems • Shares species and characteristics of both • May have more or fewer species than the ecosystems

8. Ecotones

9. Landscapes and biomes • Landscape: a cluster of interacting ecosystems • Biome: a large area of Earth with the same climate and similar vegetation • For example, grasslands can be predicted by rainfall and temperature • Boundaries grade into the next biome • Biomes describe terrestrial systems • Aquatic and wetland ecosystems are determined by depth, salinity, and permanence of water • Biosphere: one huge system formed by all living things

10. Environmental factors • Organisms live in the environment with physical, chemical, and biological factors • Some factors vary in space and time but are not used up (temperature, wind, pH, salinity) • Some factors are consumed by organisms • Water, nutrients, light, oxygen, food, space • Factors determine whether a species occupies an area

11. Optimums, ranges and limits of tolerance

12. A fundamental biological principle • Every species has an optimum range and limits of tolerance for every abiotic factor • These characteristics vary between species • Some species have a broad range • Other species have a narrower range • The range of tolerance for a factor affects an organism’s growth, health, survival, reproduction • The population density of a species is greatest where all conditions are optimal

13. Law of limiting factors

14. Habitat and niche

15. Energy changes in organisms • Breaking bonds in molecules releases energy to do work • Oxidation: a loss of electrons • Usually accomplished by the addition of oxygen (which causes burning) • Inorganic compounds are nonflammable • They have low potential energy • Production of organic material from inorganic material represents a gain in potential energy • Breakdown of organic material releases energy

16. Producers make organic molecules • Producers: make high-potential-energy organic molecules from low-potential-energy raw materials (CO2, H2O, N, P) • Chlorophyll in plants absorbs kinetic light energy to power the production of organic molecules • Green plants use the process of photosynthesis to make • Sugar (glucose—stored chemical energy) • Using inputs of carbon dioxide, water, and light energy • Releasing oxygen as a by-product

17. Within the plant • Glucose serves three purposes • It is the backbone for all other organic molecules • It provides energy to run cell activities (e.g., growth) • It is stored for future use (as starch in potatoes, grains, seeds) • Each stage of the process uses enzymes: proteins that promote the synthesis or breaking of chemical bonds

18. Cell respiration • Consumers: organisms that live on the production of others • Obtain energy from feeding on and breaking down organic matter made by producers • Respiration: organic molecules are broken down inside each cell • Produces energy for the cell to use • The reverse of photosynthesis • Oxygen is consumed • Occurs in plants and animals

19. One-way flow of energy • Most solar energy entering ecosystems is absorbed • Heats the atmosphere, oceans, and land • 2–5% is passed through plants to consumers • All energy eventually escapes as heat • Entropy is increased • Re-radiated into space • Energy flows in a one-way direction through ecosystems • Light from the Sun is nonpolluting and nondepletable • In contrast, nutrients are recycled and continually reused

20. The cycling of matter in ecosystems • Biogeochemical cycles: circular pathways of elements involving biological, geological, and chemical processes • The carbon cycle: starts with the reservoir of carbon dioxide in the air • Becomes organic molecules in organisms • Carbon is respired by plants and animals into the air or is deposited in soil • Photosynthesis in oceans moves CO2 from seawater into organisms • Respiration returns inorganic carbon to seawater

21. CO2in atmosphere Carbon Cycle Burning 5 3 Photosynthesis Cellular respiration 1 Plants, algae, cyanobacteria Higher-level consumers 2 Wood and fossil fuels Primary consumers Decomposition Wastes; death Plant litter; death 4 Decomposers (soil microbes) Detritus

22. The phosphorus cycle • Mineral elements originate in rock and soil minerals • A shortage of phosphorus is a limiting factor • Excessive phosphorus can stimulate algal growth • As rock breaks down, phosphate is released • Replenishes phosphate lost through leaching or runoff • Organic phosphate: incorporated into organic compounds by plants from soil or water • Cycles through the food chain • Broken down in cell respiration or by decomposers • Enters into chemical reactions with other substances

23. 6 Uplifting of rock 3 Weathering of rock Phosphates in rock Animals Plants Runoff 1 Assimilation 2 Detritus Phosphates in soil (inorganic) Phosphates in solution 5 Precipitated (solid) phosphates Decomposers in soil 4 Rock Decomposition

24. The nitrogen cycle • Is a unique cycle • Bacteria in soils, water, and sediments perform many steps of the cycle • Nitrogen is in high demand by aquatic and terrestrial plants • Air is the main reservoir of nitrogen (N) • most organisms can not use it

25. Plants take up nitrogen • Plants in terrestrial ecosystems (“non-N-fixing producers”) • Take up nitrogen as ammonium (NH4) and incorporate it into proteins and nucleic acid compounds • The nitrogen moves through the food chain to decomposers, releasing nitrogen wastes • Soil bacteria (nitrifying bacteria) convert ammonium to nitrate to obtain energy • Nitrate is available for plant uptake • Nitrogen fixation: bacteria and cyanobacteria can use N and produce compounds

26. Means of nitrogen fixation • Bacteria (genus Rhizobium) live in legume root nodules • The legume provides the bacteria a place to live and food • It receives a source of nitrogen in return • Nitrogen enters the food chain from the legumes • Three other processes “fix” nitrogen • Atmospheric nitrogen fixation: lightning • Industrial fixation: in fertilizer manufacturing • Combustion of fossil fuels: oxidizes nitrogen • Industrial fixation and fossil fuels release nitrogen oxides, which are converted to nitric acid (acid precipitation)

27. Denitrification • A microbial process in soils and sediments depleted of oxygen • Microbes use nitrate as a substitute for oxygen • Nitrogen is reduced (it gains electrons) to nitrogen gas • Released into the atmosphere

28. Figure 37.21 The nitrogen cycle Nitrogen (N2) in atmosphere 8 Animal Plant 6 Assimilation by plants 1 5 3 Denitrifiers Nitrogen-fixing bacteria in root nodules Nitrates in soil (NO3) Detritus Decomposers Free-living nitrogen-fixing bacteria Nitrifying bacteria 4 7 Ammonium (NH4) in soil 2

29. Comparing the cycles • Carbon is mainly found in the atmosphere • Directly taken in by plants • Nitrogen and phosphorus are limiting factors • All three cycles have been sped up by human actions • Acid rain, greenhouse gases, eutrophication • Other cycles exist for other elements (e.g., water) • All go on simultaneously • All come together in tissues of living things

30. Dynamics of natural populations • Population: a group of members of the same species living in an area • Community: populations of different species living together in an area • Populations grow with births and immigration • They decline with deaths and emigration (Births + Immigration) – (Deaths + Emigration) = Change in population number

31. Dynamics of natural populations • Population: a group of members of the same species living in an area • Community: populations of different species living together in an area • Populations grow with births and immigration • They decline with deaths and emigration (Births + Immigration) – (Deaths + Emigration) = Change in population number

32. Population growth • Population growth: change in population • Equilibrium: births + immigration are equal to deaths + emigration • Often, population growth is not zero • Population growth rate: amount the population has changed divided by the time it had to change • Population growth curves: graph how populations grow; used to find • How fast a population could grow • How many individuals there are now • What the future population size could be

33. Exponential growth • Each species can increase its population • With favorable conditions • Exponential increase: does not add a constant number of individuals for each time period • The doubling time remains constant • For example, it takes 2 days to go from 8 to 16 individuals, as well as from 1,000 to 2,000 individuals • Such growth is called an “explosion” • The population continues to grow and then dies off due to limiting resources • J-curve: the curve of exponential growth

34. Exponential growth of rabbits 500 450 400 350 300 Population size (N) 250 200 150 100 50 0 0 1 2 3 4 5 6 7 8 9 10 11 12 Time (months)

35. Logistic Growth and carrying capacity • Logistic growth: some process slows growth so it levels off near carrying capacity (K) • Results in an S-shaped curve • It levels off at K • As the population approaches K, growth slows • The population remains steady and growth = 0 • The maximum rate of population growth occurs halfway to K

36. Logistic growth of a population of fur seals 10 8 Breeding male fur seals (thousands) 6 4 2 0 1915 1925 1935 1945 Year

37. Biotic potential vs. environmental resistance • Biotic potential: the number of offspring (live births, eggs, or plant seeds and spores) produced under ideal situations • Measured by rate at which organisms reproduce (r) • Varies tremendously from less than 1 birth/year (some mammals) to millions/year (plants, invertebrates) • Recruitment: survival through early growth stages to become part of the breeding population • Young must survive and reproduce to have any effect on population size

38. Environmental resistance • Abiotic andbiotic factors cause mortality (death) • Prevents unlimited population growth • Environmental resistance: the biotic and abiotic factors that may limit a population’s increase • Biotic: predators, parasites, competitors, lack of food • Abiotic: unusual temperatures, moisture, light, salinity, pH, lack of nutrients, fire • Environmental resistance can also lower reproduction • Loss of suitable habitat, pollution • Changed migratory habits of animals

39. Reproductive strategies: r-strategists

40. Reproductive strategies: K-strategists

41. Life histories • Life history: progression of changes in an organism’s life • Age at first reproduction, length of life, etc. • Visualized in a survivorship graph • Type I survivorship: low mortality in early life • Most live the bulk of their life span (e.g., humans) • Type III survivorship: many offspring that die young • Few live to the end of their life (oysters, dandelions) • Type II survivorship: intermediate survivorship pattern (squirrels, coral) • K-strategists have a Type I pattern; r-strategists show Type III

42. Three types of survivorship curves 100 I 10 II Percentage of survivors (log scale) 1 III 0.1 0 50 100 Percentage of maximum life span

43. Predictable pattern in species • There is a predictable pattern to the way human activities affect species • r-strategists become pests when humans change an area • Houseflies, dandelions, cockroaches increase • K-strategists become rarer or extinct with change • Eagles, bears, and oaks decline

44. Community interactions

45. Species interactions • The most important relationships • Predation, competition, mutualism, commensalism • Amensalism: one species is unaffected, the other is harmed (0−) • For example, an elephant stepping on a flower or plants produce chemicals for defense against herbivory that inadvertently harms other plants • It is theoretically possible to have a (00) relationship • It has no name

46. Introduction to ecosystems • In 1988, lightning started fires in Yellowstone National Park • 165,000 acres were burned in one day • National Park Service policies have changed over time • In the early years, all fires were extinguished • Before 1988, only fires that threatened human habitations were extinguished • This fire started a great controversy over this policy • Snow in September finally put the fires out

47. Fire in Yellowstone

48. Yellowstone recovered from the 1988 fire • The fires burned 36% of the park • Burned and unburned areas were interspersed • Within 2 weeks, grasses and other vegetation sprouted • Within a year, vegetation covered the burned areas • Bison and elk fed on the new vegetation • Within 25 years, plant and animal diversity will have completely recovered in the burned areas • Fire is vital to many ecosystems • It may even impact evolution

49. Lodgepole pines growing back in the burned area of Yellowstone

50. Bison in Yellowstone