Download Principles of Biology ______Lake Tahoe Community

Principles of Biology - Biology 102
Spring Quarter
_ Written by: Sue Kloss
Lake Tahoe Community College
Instructor: Ralph Sinibaldi
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Ch. 53 Community Ecology
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I. Communities - all the organisms living in a particular area close enough for potential interaction
A. defining characteristics of a community
1. named for the dominant vegetation - influence animals that live there
a. number of plants
b. structure
2. stability -resist change and return to previous species composition after disturbance
3. trophic structure - feeding relationships
a. passage of nutrients and energy through system
4. diversity - variety of organisms that make it up
a. species richness
b. species evenness or relative abundance
1) community 1: sp. A 99, sp. B 1
2) community 2: sp. A 50, sp. B 50
II. Structural features of communities
A. Interspecific interactions - competition, herbivory, predation, symbioses (parasitism, mutualism,
commensalism)
B. interspecific competition - may eliminate a species from the community (-/- relationship)
1. competitive exclusion - Gause- 1934 - 2 species competing for the same resource can not
both exist in the same niche; one will have a competitive advantage and eventually drive the
other to extinction
a. Gause worked with Paramecium in culture
b. even a slight advantage will eventually lead to local elimination of inferior competitor
2. niche - each species has its own way to “make a living” - Chthamalus vs. Balanus
a. Chthamalus limited by competition (Fig. 53.2)
b. Balanus limited by water availability
c. niche is role in the ecosystem
1. includes ability to deal with biotic and abiotic characteristics
2. fundamental niche vs. realized niche
3. Resource partitioning - when 2 species have identical niches, and one does not become
extinct, generally one species has modified its niche to use a slightly different set of resources
a. e.g. - nuthatches vs. chickadees
b. Anolis lizards (Fig. 53.3)
4. character displacement - in two closely related spp. - when they occur in allopatric pops,
are very similar in morphology; when they occur in sympatric pops, they show larger
morphological differences (Fig. 53.4) indicating adaptation for slightly different resources when
they compete
C. intraspecific competition - natural selection
D. Predation leads to diverse adaptations in both predators and prey; (+/- relationship)
1. Predation - an interaction where one species eats another, or removes it from population
(herbivory)
a. predator - adaptations for locating and subduing prey
1. ambush predators blend in with surroundings
2. pursuers are fast and agile
b. prey - adaptations for securing prey
1. hiding, fleeing, self defense (not usually active) alarm calls to mob predator
2. animal defense against predation
a. camouflage - cryptic coloration (Fig. 53.5)
b. aposematic coloration - warning colors
c. armor, spines, quills
d. glands
e. poisons
f. mimicry
1) Batesian mimicry - palatable mimics unpalatable
a) mimics must be considerably less abundant (Fig. 53.7)
2) Mullerian mimicry - 2 unpalatables mimic each other
b) predators learn quickly not to eat anything that looks like that (Fig
53.8)
3. Herbivory - +/- when herbivore eats plants or alga
a. some are large (buffalo, moose)
b. most are small (insects, snails, sea urchins, etc)
c. adaptations - many insect herbivores have chem sensors on feet to alert them to
palatable or unpalatable food
d. many have specialized digestive systems
e. plant defenses - can’t run and hide so toxins eg. strychnine, nicotine, tannins, and
compounds that are distasteful to many herbivores - cinnamon, cloves, peppermint
1. also, spines, thorns and physical defenses like poison oak
4. parasitism (+/-) - one organism derives nutrition from host, which is harmed
a. endoparasites live within body of host
b. ectoparasites live outside of host
c. parasitoids - live in body of host and kill it
d. many parasites have multiple life stages eg. blood fluke has humans and freshwater
snails
e. some parasites cause host to do atypical behaviors that result in completion of life
cycle
for parasite
5. Disease - pathogens - disease causing agents (+/-) - bacteria, viruses, protists, fungi and
prions
a. tend to be microscopic while parasites tend to be larger, multicellular
b. cause death, while parasites often do not
6. Symbiotic relationships help structure communities
a. one species lives in or on another species
b. parasitism 1) parasites usually smaller than hosts
2) good parasites don’ t kill hosts
c. commensalism (Fig. 53.10) (+\0) relationship benefits one participant, neither hurts nor
helps the other eg. hitchhikers- barnacles on whales
d. mutualism - ants and acacias (Fig. 53.9)- changes in one likely to affect survival/repro
of the other (+\+)
e. make a table
7. Predation can maintain diversity in a community
a. Paine - 1960 - starfish in Washington’s intertidal
b. starfish removed mussels (Mytilus) from rocks below water line, allowing other
organisms (barnacles, snails, algae) the space to colonize. Cant remove all Mytilus some too large. Diversity dropped from 15 to 8.
b. keystone predator- reduces density of some of the strongest competitors in an area
8. coevolution a. a change in one species acts as a selective force in other species
b. counter adaptation in the 2nd species acts to modify first species
c. Heliconius butterfly and passionflower
1) Heliconius- enzymes to digest toxins produced by passionflower - most
other insects can’t eat it;
2) passionflower - produces 2 sugar bumps that look like eggs, Heliconius won’t
lay eggs on leaves that already have eggs.
9. Disturbance
a. helpful in maintaining diversity
b. ecological succession
1) primary
2) secondary
c. previous models had succession as linear movement to climax community
d. still has merit, but now thought of as dynamic and not necessarily linear
II. Dominant and Keystone Spp. influence on Community Structure
A. Species diversity (Fig. 53.11)
1. richness and evenness (Community a= sp. a 50% spp. b 50%
Community b = sp. a 25% spp b 75% = species A is more diverse
B. Energy flow and chemical cycling are basis of ecosystem interactions
1. energy flow is the movement of energy through components of the system
2. sunlight energy captured by plants, consumed by animals, ultimately decomposers
3. loss of energy from the system as heat
4. chemical cycling is often circular within the ecosystem
B. Trophic structure
1. transfer of energy from one trophic level to another is a food chain; arrows indicate direction
of energy flow (Fig. 53.12)
2. primary producers
3. primary consumers
4. secondary consumers
5. tertiary consumers
6. top carnivores
7. detritivores or decomposers
C. Connecting food chains are a food web (more realistic of trophic structure in an ecosystem)
1. much more complex than many textbook models (Fig. 53.13)
D. Energy supply limits the length of food chains
1. only 1% of sun energy that reaches earth is converted to biomass thru Ps.
2. primary productivity is about 180 billion tons of biomass\year (biomass = living material)
3. this is the total amount available for all organisms in all ecosystems in a year
4. Each tier of pyramid is a fraction of the level under it.
5. Laws of thermodynamics
a. Energy cannot be created nor destroyed, only transformed
b. no transformation of energy is 100% efficient (lost from system as heat)
6. At top of pyramid, not enough energy remains to support another level
7. Eating lower on the food chain
8. another factor may be stability of the chain - pop fluctuations may limit length of food chains
E. Species with large impact
1. dominant species- dominance of size, dominance of numbers (Jeffrey pines in forest, grasses in
meadows)
2. invasive species often become dominant bc no predator or pathogens (chestnut blight)
3. keystone species - control community characteristics a. starfish - Paine’s experiments- increase diversity in tide pools (fig. 53.16)
b. sea otters are keystone predators eating sea urchins which eat kelp
4. ecosystem engineers (foundation species) (Fig. 53/ 17)
a. beaver (fig. 53.18)
5. facilitators - eg. rushes allow other species to colonize in wetland areas, helps keep soil
aerated
also shades soil surface, decreasing evaporation and keeping soils nonsaline (Fig. 53.19)
F. Disturbance and Ecological succession
1. disturbance - change a community, removes individuals or resource availability etc. flood, fires,
2. not necessarily negative- patchiness is healthy - spp. diversity
3. intermediate disturbance hypothesis- encourages diversity (Fig. 53.21)
4. most healthy communities can respond quickly after disturbance (Fig 53.22)
5. most communities apparently have some form of regular disturbance
G. Human disturbance- logging, agriculture, urban development tend to reduce species diversity
H. Ecological succession
1. group of species replaced by another group of species (esp. plants) over time
2. primary - involves development of soil profile (fig. 52.23)
3. secondary - involves maintenance of existing soil, replacement of community on it
a. facilitation - early plants may be facilitators
b. inhibitors
c. tolerators
Community Ecology
OBJECTIVES
1. List the categories of interspecific interactions and explain how each interaction may affect the population
densities of the two species involved.
2. State the competitive exclusion principle.
3. Define an ecological niche and restate the competitive exclusion principle using the niche concept.
4. Distinguish between fundamental and realized niche.
5. Explain how interspecific competition may lead to resource partitioning.
6. Define and compare predation, herbivory, and parasitism.
7. Give specific examples of adaptations of predators and prey.
8. Explain how cryptic coloration and warning coloration may aid an animal in avoiding predators.
9. Distinguish between Batesian mimicry and Mullerian mimicry.
10. Describe how predators may use mimicry to obtain prey.
11. Distinguish among endoparasites, ectoparasites, and parasitoids.
12. Distinguish among parasitism, mutualism, and commensalism.
13. Explain the relationship between species richness and relative abundance and explain how both contribute
to species diversity.
14. Distinguish between a food chain and a food web.
15. Describe two ways to simplify food webs.
16. Summarize two hypotheses that explain why food chains are relatively short.
17. Explain how dominant and keystone species exert strong control on community structure. Describe an
example of each.
18. Define stability and disturbance.
19. Provide examples of how disturbance may increase or decrease species diversity.
20.
Give examples of humans as widespread agents of disturbance.
21. Distinguish between primary and secondary succession.
22. Describe how species that arrive early in succession may facilitate, inhibit, or tolerate later arrivals.
Ch. 54 - Ecosystems
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I. Ecosystem Structure and Dynamics
A. Ecosystems and physical laws
1. Laws of thermodynamics
a. energy can be neither created nor destroyed, only transformed
b. in any transformation, there is always some inefficiency - energy lost as heat
B. Ecosystem – biotic community and abiotic environment (Fig. 54.1)
1. Energy flow is linear – eventually all energy is released as heat (less organized)
Chemical cycling is circular –chemical elements are cycled between living and nonliving components
a. plants acquire them in inorganic form from atmosphere/soil and fix them into organic molecules
b. microbes break down dead organism and return the components in inorganic form to air/soil
C. Trophic structure is key factor in ecosystem dynamics
1. trophic structure – transfer of food from level to level is food chain –(Fig. 54.2)
2. this doesn’t ever really happen like this – its much more complex = food web
3. arrows move in the direction of energy flow
a. Producers are autotrophs – Ps or Chemosynthesis
b. Primary consumers eat autotrophs. E.g grasshopper
c. Secondary consumers eat primary consumers
d. Tertiary consumers eat consumers from the levels below
e. Quaternary consumers – eat other 3 levels of consumers
f. Detritivores – dead material produced by all levels – animal wastes, plant litter, carrion
1. rodents, earthworms, crayfish, crabs, vultures, as well as fungi and prokaryotes
2. decomposition – turning organic matter into inorganic matter – we all do it, but prokaryotes and fungi
decompose less usable material and make it available to all of life
3. food chains are an over simplification ; interrelated food chains are called food webs
II Physical and chemical factors limit primary production in ecosystems
A. Ecosystem energy budgets
1. Of all the visible light that strikes earth, only about 1% is converted to chemical energy in Ps
2. Gross primary production (GPP) = the amt of light energy that is converted to chemical energy by Ps
a. Net Primary production (NPP) = the amt of GPP - Respiration - R- of primary producers
b. for example, forests may have NPP only 25% of GPP; can be expressed in g/m2/yr (dry wt)
c. different ecosystems have Different NPP (Fig. 54.4)
d. satellite images can give us info about global NPP (Fig. 54.5)
3. Limiting factors are factors that must be added for productivity to increase; in L. Tahoe, it’s P limited
a. eutrophication - increased nutrients so that there’s more available food for organisms
1. can be useful - upwelling
2. can turn oligotrophic lakes into algal filled lakes - (Fig. 5.7)
III. Energy transfers btn trophic levels are usually less than 10% efficient
A. Energy Supply limits length of food chain
1. every day, earth receives about 100 million atomic bombs worth of solar energy
a. absorbed
b. reflected
c. refracted
2. only 1% converted to chemical energy (Ps)
a. in one yr, this is enough to produce 170 billion tons of biomass each year
b. primary production – turning solar energy into chemical energy
c. only 1/6 the energy eaten in the leaf gets incorporated into caterpillar biomass- what happens
to res?
(Fig. 54.10)
3. different ecosystems produce wildly varying amts of biomass
a. open ocean has very low production but large;
b. tropical rain forests have only 5% of ocean’s area, but produce almost as much
d. pyramid of energy (Fig. 54.11)
e. 10% avg. of energy is transferred up, differs among ecosystems – from 5 – 20%
f. explains why top level consumers need much bigger home range- it takes a lot of vegetation to
support so many trophic levels
g. so limited biomass at top of pyramid is concentrated in relatively small number of large individuals
who need large areas
h. no wonder that many face extinction
i. not enough energy at top of pyramid to support another level
B. This is why meat is a luxury for humans and why ecologically it is better to eat lower on the food chain (Fig.
54.14)
C. Pyramid of numbers - most predators are larger than prey (not always, think of insects in trees) (Fig. 54.13)
D. Green world hypothesis
1. with so many consumers, how can many terrestrial ecosystems support large, standing crops?
2. green world hypothesis - terrestrial herbivores held in check by predators, parasites, disease (Fig. 54.15)
a. how green is the world? approx. 83 x 1010 metric tons of C are stored in plant biomass
b. production is about 5 x 1010 metric tons/yr in terrestrial ecosystems
c. herbivores consume annually less than 17% of primary productivity annually
3. green world hypothesis proposes factors that keep herbivores in check a. Plants have defenses vs. herbivores
2.
b. nutrients, not energy supply, typically limits herbivores
c. abiotic factors limit herbivores (unfavorable temp/moisture for herbs, etc., keeps them at a level far
below K)
d. intraspecific competition limits herbivores
e. interspecific competition limits herbivores
IV. Biological and geochemical processes move nutrients between organic and inorganic parts of ecosystems
A. Chemicals are recycled between organic matter and abiotic reservoirs
1. no extraterrestrial sources of food or water, so life depends on recycling of chemicals
2. We will look at 4: water, carbon, nitrogen and phosphorous
3. Chemicals pass back and forth btn organic matter and abiotic components of ecosystems (Fig. 54.16)
4. If chemical is stored in large amts outside of living organisms, this is called abiotic reservoir or a sink
B. Water moves thru biosphere in global cycle – see fig. 54.17
1. water from pacific ocean may end up in animal’s body far inland in N. America
2. human activity affects water cycle
a. destruction of rain forest
b. pumping up of ground water
c. irrigation
C. Carbon Cycle depends on Ps and Respiration
1. increased burning of wood and fossil fuels is putting more CO2 into air
a. global warming
D. Nitrogen cycle relies on bacteria
1. atmosphere is huge N sink – N2
2. nitrate (NO3) and ammonium (NH4) needed by plants, produce by bacteria from N2
3. plants called nitrogen fixers have root nodules for bacterial symbiosis
4. human activities –
a. sewage plants increase N in water bodies
b. N fertilizers end up in water
c. Algae grow in water bodies, kill fish
d. Nitrates in groundwater convert to nitrites, toxic to humans – Salinas area
E. Phosphorus cycle depends on weathering of rock 1. main sink is in rocks
2. same is true of K and Ca
3. slow weathering of rocks adds Phosphates to soil, absorbed by plants and added to biomass for food
chain
4. human activities –
a. fertilizers w/P increase algal growth
b. sewage tment increases P wastes
F. Decomposition may limit nutrient cycling rates (Fig. 54.18)
G. Ecosystem alteration can upset chemical cycling – Hubbard Brook
1. clear-cut and sprayed to prevent plant growth –
a. water runoff increased 30-40% - no plants to cycle it
b. net losses of nutrients- huge Fig. 54.19
c. nitrate drained out of system; water levels had unsafe amts for humans
d. no Ca ions- leached out- no plant growth as of 1996
V. Human Population is disrupting chemical cycles throughout the biosphere
A. Nutrient enrichment - Agriculture and nitrogen cycling
1. different types of systems hold nutrients for different lengths of time
a. temperate prairie (North America - many years) vs. tropical forests (2 yrs or so)
b. humans have huge imputs of especially N (approximately doubled earth’s version of fixed N)
1. NO x contribute to atmospheric warming, depletion of Ozone, acid rain)
2. Contamination of aquatic ecosystems
a. plants can absorb some amt. of nutrient in ecosystem without damage
b. after that, they leach into ground water and runoff into aquatic systems
1. contaminate water supply
2. choking water ways
3. kill aquatic life
B. Acid Precipitation - burning wood/petroleum - rel. SO x and NO x
1. Acid precip has pH < 5.6 (Fig. 54.21, 22)
a. some storms have pH < 3
b. damages plants, alters chemical stores and cycling in soils and aquatic systems, esp.
freshwater
C. toxins in the Environment
1. Biological magnification
a. endocrine disrupters - PCBs. (Fig. 5.23)
1. in gull eggs, 5000 x greater than phytoplankton
b. DDT, etc.
D. Carbon Dioxide in atmosphere (Fig. 54.24)
1. global warming and greenhouse effect - CO2 and water vapor- transparent to light, absorb IR as heat
2. migration of plants and animals may not occur = speed of global warming
E. depletion of Ozone (Fig. 54.26, 27)
Ch. 54 Objectives
1. Describe the fundamental relationship between autotrophs and heterotrophs in an ecosystem.
2. Explain how the first and second laws of thermodynamics apply to ecosystems.
3. Explain how decomposition connects all trophic levels in an ecosystem.
4. Explain why the amount of energy used in photosynthesis is so much less than the amount of solar energy that reaches
Earth.
5. Define and compare gross primary production and net primary production.
6. Define and compare net primary production and standing crop.
7. Compare primary productivity in specific marine, freshwater, and terrestrial ecosystems.
8. Explain why energy is said to flow rather than cycle within ecosystems.
9. Explain what factors may limit production in aquatic ecosystems.
10. Describe an experiment that provided evidence that iron availability limits oceanic primary production in some regions.
Explain how iron availability is related to nitrogen availability in these regions.
11. Explain why areas of upwelling in the ocean have exceptionally high levels of primary production.
12. Distinguish between each of the following pairs of terms:
a. primary and secondary production
b. production efficiency and trophic efficiency
13. Explain why the production efficiency of a human is much less than the production efficiency of a mosquito.
14. Distinguish among pyramids of net production, pyramids of biomass, and pyramids of numbers.
15. Explain why aquatic ecosystems may have inverted biomass pyramids.
16. Explain why worldwide agriculture could feed more people if all humans consumed only plant material.
17. Explain the green-world hypothesis. Describe five factors that may act to keep herbivores in check
18. Describe the four nutrient reservoirs and the processes that transfer the elements between reservoirs.
19. Name the main processes driving the water cycle.
20. Name the major reservoirs of carbon.
21. Describe the nitrogen cycle and explain the importance of nitrogen fixation to all living organisms. Name three other
key bacterial processes in the nitrogen cycle.
22. Describe the phosphorus cycle and explain how phosphorus is recycled locally in most ecosystems.
23. Explain how decomposition affects the rate of nutrient cycling in ecosystems.
24. Describe how net primary production and the rate of decomposition vary with actual evapotranspiration.
25. Describe the experiments at Hubbard Brook that revealed the key role that plants play in regulating nutrient cycles.
26. Describe how agricultural practices can interfere with nitrogen cycling.
27. Explain how “cultural eutrophication” can alter freshwater ecosystems.
28. Describe the causes and consequences of acid precipitation.
29. Explain why toxic compounds usually have the greatest effect on top-level carnivores.
30. Describe how increased atmospheric concentrations of carbon dioxide could affect Earth.
31. Describe the causes and consequences of ozone depletion.