Energy and Living Things

1. Energy and Living Things

2. Outline • Energy Sources • Solar-Powered Biosphere • Photosynthetic Pathways • Using Organic Molecules • Chemical Composition and Nutrient Requirements • Using Inorganic Molecules • Energy Limitation • Food Density and Animal Functional Response • Optimal Foraging Theory

3. Energy Flows Through Living Systems Heterotrophs Plants= Autotrophs

4. Autotroph: ‘self feeder’ - an organism that can gather energy (usually from light) … to store in organic molecules • Photosynthesis • chemosynthesis • Heterotroph: An organism that must rely on other organisms to capture light energy … must rely on breakdown of organic molecules produced by an autotroph as an energy source • Classified by trophic level

5. Law of the minimum- ecosystems must adapt to it. • Light in ocean floor • Water in desert • Heat on mountain top • Matter is also limiting, thus have limiting nutrients that allow for life

6. Flow of energy and nutrients • Photosynthesis • Metabolism

7. Photosynthesis Capture and transfer light energy to chemical bonds Occurs in: Plants Algae Certain Bacteria Not a perfect process – some energy is lost - entropy

8. How Photosynthesis Works • Light strikes leaf • Energy absorbed by chemical pigments • Absorbed energy drives chemical processes to convert CO2 into larger molecules • Energy absorbed in building larger molecules, released as they are broken down

9. Only certain Wavelengths of Light are Used in Photosynthesis • Light Energy Used = ‘Photosynthetically Active Radiation’ or PAR • How Much is absorbed: Number of light energy (photons) striking square meter surface each second. • Chlorophyll absorbs light as photons. • Landscapes, water, and organisms can all change the amount and quality of light reaching an area. • Light not absorbed is reflected • Some in PAR + all in green and yellow wavelengths

11. Wavelengths most useful in driving photosynthesis Absorption spectra of chlorophylls and carotenoids Wavelengths not used - reflected

12. Fall color • In many plants production of chlorophyll ceases with cooler temperatures and decreasing light • other pigments become visible

13. C3 Photosynthesis CO2 enters passively so stomata have to be open for long periods of time

14. Why C3 Photosynthesis Doesn’t always work out - CO2 must enter though stomata • stomata (sing., stoma) are tiny holes on the undersides of leaves • CO2 enters and moisture is released • In hot, dry climates, this moisture loss is a problem

15. Food Web Producers • Herbivores • Animals that eat plants • The primary consumers of ecosystems • Green plants and algae • Use solar energy to build energy-rich carbohydrates • Carnivores • Animals that eat herbivores • The secondary consumers of ecosystems • Omnivores are animals that eat both plants and animals • Tertiary consumers are animals that eat other carnivores • Detritivores • Decomposers • Organisms that break down organic substances • Organisms that eat dead organisms

16. Thermodynamics • Total amount of energy kept constant • Energy can be converted

17. Transfer of Energy with Ecosystems • Board notes

18. Three Feeding Methods of Heterotrophs: • Herbivores: Feed on plants. • Carnivores: Feed on animal flesh. • Detritivores: Feed on non-living organic matter.

19. Classes of Herbivores • Grazers – leafy material • Browsers – woody material • Granivores – seed • Frugivores – fruit • Others – nectar and sap feeders • Humming birds, moths, aphids, sap suckers …

20. Herbivores • Substantial nutritional chemistry problems. • Low nitrogen concentrations – difficulty extracting needed protein/amino acids from source. • Require 20 amino acids to make proteins ~ 14 are must come from diet

21. How do plants respond to feeding pressures by herbivores? • Mechanical defenses – spines • Chemical defenses • Digestion disrupting chemicals – tannins, silica, oxalic acid • Toxins – alkaloids • More common in tropical species How do animals respond? • Detoxify • Excrete • Chemical conversions – use as nutrient

22. Carnivores • Predators must catch and subdue prey - size selection. • Usually eliminate more conspicuous members of a population (less adaptive). • act as selective agents for prey species.

23. Adaptations of Prey to being preyed upon • Predator and prey species are engaged in a co-evolutionary race. • Avoid being eaten – avoid starving/becoming extinct • Defenses: • Run fast • Be toxic – and make it known • Pretend to be toxic • Predators learn to avoid

24. Carnivores • Consume nutritionally-rich prey. • Cannot choose prey at will. • Prey Defenses: • Aposomatic Coloring - Warning colors. • Mullerian mimicry: Comimicry among several species of noxious organisms. • Batesian mimicry: Harmless species mimic noxious species.

25. Mullerian mimicry: Comimicry

26. Batesian mimicry: Harmless species mimic noxious species

27. Aposomatic Coloring - Warning colors

29. Detritivores • Consume food rich in carbon and energy, but poor in nitrogen. • Dead leaves may have half nitrogen content of living leaves. • Fresh detritus may still have considerable chemical defenses present.

30. Detritivores and decomposers

31. productivity • Refers to the production of food • Primary production = total gross primary production • Activity- Compare ecosystems p. 26

32. Optimal Foraging Theory • Assures if energy supplies are limited, organisms cannot simultaneously maximize all life functions. • Must compromise between competing demands for resources. • Principle of Allocation • Fittest individuals survive based on ability to meet requirements principle of allocation

35. Optimal Foraging Theory • All other things being equal,more abundant prey yields larger energy return. Must consider energy expended during: • Search for prey • Handling time • Tend to maximize rate of energy intake. • What would a starving man do at an all you can eat buffet?

36. Optimal Foraging in Bluegill Sunfish

37. Cycles of matter • Nitrogen • Carbon

38. Nutrient Cycling and Retention Chapter 19

39. Nitrogen Cycle • Includes major atmospheric pool - N2. • Only nitrogen fixers can use atmospheric supply directly. • Energy-demanding process. • N2 reduced to ammonia (NH3). • Once N is fixed it is available to organisms. • Upon death of an organism, N can be released by fungi and bacteria during decomposition.

40. Nitrogen fixation Biological Nitrogen Fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by a pair of bacterial enzymes • N2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi

41. Microbes Denitrification NO3- (nitrate) → NO2- → NO → N2O → N2 gas Nitrogen Cycle

42. Carbon Cycle • Moves between organisms and atmosphere as a consequence of photosynthesis and respiration. • In aquatic ecosystems, CO2 must first dissolve into water before being used by primary producers. • Although some C cycles rapidly, some remains sequestered in unavailable forms for long periods of time.

43. Carbon Cycle

44. Animals and Nutrient Cycling in Terrestrial Ecosystems • Huntley and Inouye found pocket gophers altered N cycle by bringing N-poor subsoil to the surface. • MacNaughton found a positive relationship between grazing intensity and rate of turnover in plant biomass in Serengeti Plain. • Without grazing, nutrient cycling occurs more slowly through decomposition and feeding of small herbivores.

45. Animals and Nutrient Cycling in Terrestrial Ecosystems

46. Plants and Ecosystem Nutrient Dynamics • Fynbos is a temperate shrub/woodland known for high plant diversity and low soil fertility. • Two species of Acacia used to stabilize shifting sand dunes. • Witkowski compared nutrient dynamics under canopy of native shrub and introduced acacia. • Amount of litter was similar, but nutrient content was significantly different. • Acacia - N fixer

47. Biotic communities

48. Climate and weather