Biology 1407 Notes Exam 5 - Ecology Ch 34, 37, 38
Ecology - the study of how organisms interact with their environment; interactions occur
at several levels and include both living (biotic) and nonliving (abiotic) factors
34.1
Communities
Ch 37
Set of populations living together and interacting in a particular area
- coevolved and coadapted set of populations
- communities have some emergent properties:
1. species diversity (complexity)
37.10
- measure of variety of populations in the community
- species richness - total number of species
- relative abundance - how even the mix of species.
- monocultures have low diversity
- most agricultural systems
- very vulnerable to pest and diseases
- diversity is the results of interactions among the population adapting to each
other.
- 4 types of interactions are important in shaping community:
- interspecific competition (several species trying to get the same resource) - / -
37.1-.3
- competitive exclusion principle - two species with the same niche cannot
coexist; one will go extinct or populations will adapt to slightly different niches
- resource partitioning - character displacement - an interesting twist is that predation may be important in reducing competition.
see 37.11
- herbivory - animals eating plants
+/37.6
- herbivores adapt by increased senses to locate plants, feeding behaviors and
anatomy and physiology to process and digest plant
- plants evolve defenses - mechanical (thorns, hairs, tough cell layers, etc.),
chemical (toxins, noxious taste) and behavioral (timing of fruit production,
mimicry, etc.)
- plants and herbivores coadapt and “shape each other”
- predation - one species (predator) kills and eats another species (prey). + / - predator and prey become very specialized coevolving and adapting.
37.5
- predators evolve to be better at catching prey
- those individuals that are the best leave more offspring with their genes.
- sharper senses, physical improvements that increase speed and agility,
more effective catching devises, better search behavior, etc.
- prey evolve to be better at not being captured
- those individuals that are the best at not being captured leave more
offspring with their genes.
- sharper senses, physical improvements that increase speed and agility,
mechanical and chemical defenses, cryptic or deceptive
coloration, escape behaviors, mimicry, etc.
- predator-prey interactions not only increase complexity in the community, but
also help stabilize the community.
- they frequently become density dependent regulating factors for each
other
- predators, called keystone species, reduce the competition among
several prey species. Explain how this works.
37.11
- symbiosis - two species with a very close coevolved relationship, coadapted:
- parasitism
+/37.7
- one species (parasite) benefits and the other (host) is harmed, but usually
not killed; coadapt to each other
- develop complex life cycles in relation to each other
- develop stable relationship with relatively healthy host
- examples - commensalism
+/0
- one species benefits and the other is not affected.
- may not be common in nature
- examples - mutualism
+/+
37.4
- both species benefit, they may even depend on each other.
- very important in the history of life, many examples with major impacts
on life
- examples -
Biodiversity is a measure of the variety of life
37.13, 38.1 - .2
- genetic variation is variation of genes (traits) within a population, allows
adaptation
- species diversity is complex mixture of species within a community, may be
important in community stability
- ecosystem diversity is variation of major communities (biomes) with many
smaller ecosystems
*All of these have decreased significantly in the last few decades. Describe the three
major causes.
38.1 - .2
*Why is biodiversity important to humans?
*10,000 years ago humans and domestic animals accounted for less than 0.1% by weight
of all vertebrate life on land and in the air.
Today it is about 98% (3/4 is livestock and pets)
2. stability - a community’s response to disturbance
-resistance to change, or recovery after change
37.12
- ecological succession is recovery when disturbance occurs
- the community goes through a series of changes where species replace
each other as conditions change
- primary succession begins after severe disturbance, where no soil exists
- first organisms to move in are “pioneer” species, species that can exist in
harsh environments
- the species diversity is very low, only a few species can withstand the
harsh conditions, so the community is simple
- the trophic structure is a food chain
- the species present usually have opportunistic (r-selected) life histories
- as these first species live and die the environment becomes modified, soil
begins to form, and other species are able to become established.
- secondary succession begins after moderate disturbance in which the soil is intact
(fires, floods, etc.)
- species diversity increases, community becomes more complex
- the trophic structure is more complex, becomes a food web
- the species present in later succession stages usually have equilibrium
(k-selected) life histories
- the climax community is the final stage that will exist until the next
disturbance
- disturbance may be routine in some communities, so that the probable climax
community never develops
The relationship between diversity and stability of communities is not well understood;
diverse communities have been thought to be more stable but this idea is changing.
Controlled scientific experiments on a community scale are difficult.
*Why might studying ecological succession be difficult?
3. prevalent form of vegetation (dominant species)
- structure of the community, structural features of the vegetation
- major associations of plants and animals are called biomes
- has a typical structure, type vegetation
*What is convergent evolution?
37.1, 34
- the kinds of plants that exist in a community depends on organisms ability to
adapt to a set of environmental conditions.
- the kinds of animals present in the community frequently depends on the plants
that are present.
- many factors are important in determining the community that develops in a
particular place:
- the climate (amount of light, water, temperature, wind, soil, etc.)
- the two most important are temperature and moisture
- several factors determine the distribution of temperature and moisture, primarily
by variation in energy from the sun (photons / area)
34.5
- Earth’s tilt determines seasons
- effect of latitude on distribution of temperature and moisture
- effect of the “rain shadow”
- effect of elevation
The relationship between the biome present and temperature and moisture can be plotted
in a biome distribution graph with temperature (or latitude or altitude) on the Y axis and
the amount of moisture on the X axis.
See 34.6 - .17 for descriptions of the major terrestrial biomes and “Applying the
Concepts” Ch 34 for a climograph
Place each of the major climatic regions and each of the following biomes in the
appropriate place in the temperature / moisture graph (climograph):
climatic regions: tropic, temperate, polar (subarctic, arctic)
biomes: tropical forest, savanna, desert, chaparral, temperate grassland, temperate
broadleaf forest, taiga (coniferous forest), tundra
Describe the key features of each biome.
4. Trophic structure - feeding within community - what species feed on what species.
- food chain linear sequence of eating (algae--> minnow---> sunfish)
37.8
- food web is interconnected food chains, more complex arrangement
- food webs are more efficient and may be more stable. Why?
37.9
- Several levels can be recognized in relation to the production of food (organic
material):
- producers – photoautotrophs (photosynthetic - plants, algae, bacteria) and
chemoautotrophs (bacteria) that make organic material from inorganic
- consumers - heterotrophs that feed on organic matter (animals, fungi, bacteria)
producers ---> primary consumer ---> secondary consumer ---> tertiary consumer
---> quaternary consumer
( a consumer may feed at several levels)
- decomposer - consumers that feed on dead organisms and organic detritus from
all trophic levels (detritivores)
Ecosystems
37.14 - .23
- all living organisms (the community or biotic part) and their physical environment
(the abiotic part)
37.14
- Two properties of ecosystems are important:
- energy flow through the ecosystem (not reused)
- chemical nutrient cycling (nutrients reused)
- both of these involve the trophic structure since food is chemical energy and
chemical nutrients.
Energy in as light energy, through community as chemical energy, out as heat
energy - one way flow
Chemical nutrients in as low energy inorganic chemicals, through as high energy
organic chemicals
Some terms relating to energy flow and nutrient cycles:
37.15 - .17
- biomass - organic material that composes plant and animal bodies (mass
of living organisms) mass/area
ex. grams/square meter
- standing crop biomass - biomass present at one time in the ecosystem
- biomass is also chemical energy since energy is stored in the chemical
bonds
- production or productivity - rate of making biomass
- biomass per time and area. ex. grams / m2 year
- primary productivity - rate biomass is produced by producers
(autotrophs)
- gross primary productivity (GPP) - the rate at which organic
molecules are made; equal to the total photosynthesis of
producers.
- net primary productivity (NPP) - the biomass = not used by the
producers in cellular respiration.
- this is the biomass that producers use to grow; it adds biomass to
plants and is the stored chemical energy that is available to
heterotrophs as food.
- NPP = GPP - cellular respiration
- NPP = about 50% of GPP in most ecosystems (may range higher)
- the ratio of photosynthesis to cellular respiration is about 2 in most ecosystems.
(photo / cell. resp. = 2)
- productivity depends on growing conditions for producers - light intensity,
temperature, moisture available, availability of nutrients, etc.
- secondary productivity - rate (biomass per time and area) that consumers
and decomposers (the heterotrophs) convert biomass (their food)
into new biomass (their growth and reproduction).
- animals are about 10% efficient at secondary production, also
called ecological efficiency.
- variable 5 – 20% depending on the food they eat.
pyramids represent trophic levels:
standing crop biomass pyramids
- biomass in the different levels of the trophic structure at one time
*How are these pyramids misleading?
*Draw two examples.
energy pyramids
37.16 - .17
- productivity of different levels of the trophic structure
- these tell us more than biomass pyramids because they show the rate biomass
is produced.
*Draw an energy pyramid.
*Why do most ecosystems have fewer than 5 trophic levels?
*What is the implication of this to the human population?
37.17
*How does this relate to harvesting resources and maximum sustainable yield?
*How does this relate to the ecological footprint?
*Vegetarian diet uses 300 gal water per day, omnivorous diet uses 4,000 gal water / day.
Biogeochemical cycles
37.18 - .22
- movement of chemicals through living (biotic) and nonliving (abiotic - atmosphere,
soil, rocks, etc.) parts of ecosystem
some primary nutrients:
water*
oxygen
hydrogen
(see table 2.1 for nutrients)
nitrogen*
phosphorus*
calcium
* = nutrients that can be limiting
carbon
potassium
sulfur
Biological magnification
38.2
*What is this and why is it important to humans?
*half-life of PCB in humans is about 10 years
*1,000 tons mercury added to environment each year
The carbon cycle
37.19
- the abiotic source of carbon (the inorganic) is the atmosphere in the form of CO 2
- carbon is also in rocks (limestone is the most common rock type CaCO 3 )
- the metabolic process of photosynthesis converts inorganic carbon into organic carbon
(glucose, proteins, etc.)
- carbon is passed from organism to organism as organic molecules (food through trophic
levels).
- the metabolic process of cellular respiration converts organic carbon into inorganic
carbon
- the chemical process of combustion converts organic carbon (may be fossilized) into
inorganic carbon.
- fossilization of organic material slows carbon cycling.
- explain how the carbon cycle has become unbalanced in the past few decades and how
this relates to the greenhouse effect.
38.3 - .6
- 100 tons (200,000 pounds) of ancient plant life to produce 1 gallon gasoline – 422 years
for gas in 1997.
- draw the carbon cycle:
atmosphere
P
CR
limestone
C
plants
fossil fuels
CR
animals
CR
decomposers
The nitrogen cycle:
Why is nitrogen important to living organisms?
37.21
- the abiotic source of nitrogen is the atmosphere (about 80% of air is N 2 ) but the nitrogen
molecule N2 cannot be used by plants or other organisms. N-N
(triple bond)
- nitrogen fixation is converting N 2 to a usable form such as ammonium NH4 + or nitrate
NO3 - only a few species of bacteria can do this - the nitrogen fixing bacteria and
cyanobacteria convert nitrogen to ammonium.
- nitrifying bacteria in the soil convert ammonium to nitrates.
- denitrifying bacteria convert nitrates back into nitrogen.
- plants use nitrates and ammonium to make proteins and other organic molecules.
- organic nitrogen (proteins) passes through the community (trophic levels) as food.
- decomposers convert organic nitrogen (proteins) to inorganic ammonium in the process
of decomposition or ammonification. This makes nitrogen available to plants again.
- during the last century the industrial process has been developed to convert atmospheric
nitrogen into nitrates and ammonia. This requires considerable energy but allows
us to increase agricultural yields.
- Draw the nitrogen cycle:
atmosphere
N2
nitrogen fixing
bacteria
NH3 -
decomposers
animals
nitrifying
protein
protein
bacteria
NO3
plants
N2
denitrifying
bacteria
N2
industrial
process fertilizer
Describe how the nitrogen cycle has become unbalanced in the last century:
37.22
- cultivation generally decreases organic material in soil and soil structure.
- fertilizers are frequently over-applied and wash into streams and lakes.
- produces eutrophication and “dead zones”.
How?
Global warming / climate change
- heat content of object result of balance of energy in and energy out
- all objects with heat radiate energy in relation to temperature
- biosphere gaining about 2 watts / square meter
38.3 - .6
- properties of water related to heat energy
- water vapor strong greenhouse gas, amount directly related to water
temperature
- heat energy into temp. rise or change of state (ice <---> liquid water <---> vapor)
- any factor that changes heat balance called "forcer"
- change in heat content balance of forcers
- sensitivity of forcer is how effective it is
- gases in atmosphere absorb and radiate heat - greenhouse gases
- Earth surface average temp. without greenhouse gases would be about 0 0 F (570
F with)
- several gases have high sensitivity
- past climates can be studied, related to forcers
- 400,000 + years of ice cores from Vostoc, Antarctica shows relationship between
CO 2 and global temp.
- greenhouse gases ( CO 2 and methane ) important in past climate changes
Potential feedbacks that may speed global warming :
- release of methane hydrates from sea floor
methane 25 times more potent than CO 2
- decomposition of thawing permafrost
permafrost 20% of Earth surface
700 ppb in late 1700’s – 1800 ppb in 2000
- drying of Amazon rainforest
- acidification of oceans
50 time more CO 2 in ocean than in air
less soluble in acidic water
- decreased reflectivity (albedo) of ice cover
- less heat absorption in melting ice
Biology 1407 Exam 5 Review Ch 34, 37, 38
Community - define the term and tell what coadapted or coevolved means.
What is species diversity (complexity)? - define the term and list 3 types of interactions that cause it.
What is the difference between species richness and relative abundance?
Define the term competition and distinguish between intraspecific and interspecific. What
does each cause?
Define and give an example of the competitive exclusion princip le and resource partitioning.
Define the term predation and describe its effect on the predator and prey species and on
the community. What are keystone species and how do they affect the community?
What is herbivory? Describe some of the effects of herbivory on plants and animals.
Define the term symbiosis and distinguish between parasitism, commensalism and
mutualism. Give examples of each.
What is biodiversity and how has it changed in the last century?
Describe the 2 different ideas of stability. Define the term ecological succession.
Distinguish between primary and secondary ecological succession and give the key
features of communities in each stage.
What is the climax community and why may this never develop?
What do biologists mean by community structure (dominant form of vegetation) - What
are the 2 most important factors determining this? Describe why these two factors are
distributed unevenly on Earth. What are the effects of latitude and altitude?
List the major biomes of the world and show how they are related to temperature and
moisture by drawing a climograph with these biomes in the correct position.
What is the trophic structure - define and distinguish between food chains and food webs. What are the
advantages of food webs?
Distinguish between producers, consumers (several levels) and decomposers. Give
examples (where do each of these levels get their food).
Ecosystems - define the term and distinguish between the biotic and abiotic parts.
How is the trophic structure related to energy flow?
Define and distinguish between biomass and primary productivity; between gross (GPP)
and net primary productivity (NPP). Which is largest?
Distinguish between primary and secondary productivity. What is ecological effic iency?
Distinguish between standing crop biomass pyramids and energy pyramids.
Why do most ecosystems have 5 or fewer levels and what is the implication of this to humans?
What is biological magnification and why is this important to humans?
How is chemical cycling (biogeochemical cycling) related to the trophic structure?
List some important nutrients that cycle - which are frequently limiting resources?
Draw the carbon cycle, including the processes and the forms involved. Explain how the carbon c ycle has
been altered in the past few decades. Describe the greenhouse effect.
Draw the nitrogen cycle, including the processes and the forms of nitrogen involved.
If the atmosphere is 80% nitrogen, why is nitrogen frequently a limiting factor?
How has human activity altered the nitrogen cycle?
Describe some possible feedback processes that could significantly speed global climate change.