Download eco chpt 3

Ecology
Study of interactions between organisms
and their environment
The living environment
A. The biosphere is the portion of the earth that
supports life
i. Extends from high in the atmosphere (air) to
the bottom of the oceans (and includes
underground)
ii. It is comparable to the outer skin of an
apple
iii. Many different environments exist in it
B. All the living organisms that inhabit an
environment are called biotic factors (they are all
found in the biosphere)
C. Different organisms are adapted to different parts
of the biosphere
4. The non-living environment
A. Ecologists study how the non-living factors in an
environment affect the living things
i. abiotic factors have obvious effects on living
things and often determine which species
survive in a particular environment
B. Non-living factors are called abiotic factors
i. Ex. Air, moisture, light, and soil
Levels of Organization: The Hierarchy of Life
1. All organisms depend on other organisms
A. Organisms don't live in isolation
i. organisms depend on each other directly or
indirectly for things like food, shelter,
reproduction etc.
ii. you can't just study one organism and
understand everything about that organism
B. Ecologists study the individual, how it interacts
with its same species (organisms of the same type that
can interbreed and produce fertile offspring), how it
interacts with different species, and how it is affected
by abiotic factors
2. Interaction within populations
A. Population is a group of the same specie in the
same place at the same time that interbreed
B. Members of a population compete with each other
for food, mates, and other resources (competition)
i. This determines how far apart populations
are from each other and how large populations
become
ii. Competition occurs constantly; whether
resources are in short supply or not
C. Some species have adaptations that reduce
competition within a population
i. Ex. - Frogs and tadpoles don't compete;
they live in different habitats and have
different food supplies
3. Individuals interact within communities
A. A community is a group of interacting populations
B. A change in one population will affect other
populations
i. This affect can be large or small, direct or
indirect
4. Interactions between living things and abiotic factors form
ecosystems
A. Terrestrial ecosystems - on land
B. Aquatic ecosystems - in water (fresh or salt)
i. Marine ecosystems occupy approx. 70% of
the earths surface
*A group of ecosystems with similar climates and organisms
is referred to as a biome
*the entire portion of the Earth that supports life is called the
biosphere
5. Where and how organisms live
A. Every specie has a particular function in its community
B. A niche is the role the specie plays in the community
i. The space, food, and other conditions and organism
needs to survive and reproduce are part of its niche
ii. It also includes how the specie affects its environment
C. Two species can't exist for ling if their niches are the same
i. one of the species will gain control and the other specie
will either die out, leave, or find a new niche (competitive
exclusion principle)
ii. unique adaptations and structures are important
because they reduce the competition with other species in
the same habitat
D. A habitat is the place where an organism lives
i. habitats can change or even disappear
due to both natural and human causes
E. Several species may share the habitat
i. But the food, shelter and other resources
of that habitat are divided into separate
niches
Species Relationships
1. Feeding relationships
A. Reflects an organisms niche within the community
B. Autotrophs
i. Make their own (food) from the sun or
stored energy in chemical compounds
ii. The sun is the ultimate source of energy for life,
but that energy must be converted to a useable
form for organism
iii. Also called producers because they produce
their own food
iv. Plants are the most common, some algae and
bacteria also
v. All other organisms depend on autotrophs for
their nutrients and energy
*Photoautotrophs – use the sun and carbon (from
the atmosphere) to make carbohydrates (food
energy) in a process called photosynthesis
*chemoautotrophs – use chemical energy (not the
sun) to make carbohydrates (food energy) in a
process called chemosynthesis
***We will deal with photoautotrophs in this course.
C. Heterotrophs
i. Organisms that depend on autotrophs for their
nutrients and energy are called heterotrophs
ii. Don't produce their own food
iii. They must get their energy from consuming other
living things, therefore they are also known as
consumers
iv. There are a variety of feeding relationships (what eats
what)
a. Herbivores
1. feed on plants
b. Carnivores
1. feed on other animals
c. Omnivores
1. feed on both plants and animals
d. Scavengers
1. feed on dead organisms and garbage
2. play an important roll in the environment,
they are the cleanup crew
e. Decomposers
1. break down complex compounds of dead and
decaying plants and animals
2. many bacteria, protozoa, and fungi
f. Detritivores - feed on decaying matter
Matter And Energy In Ecosystems
1. Matter and energy flow through the ecosystem
from organism to organism
A. Matter starts with a producer and then
moves through the different consumers and
finally to decomposers, who return it back to
the soil in a broken down form so the
producers can start the cycle all over again.
B. The amount of energy that is passed on at
each level is only 10%. The rest is either used
by the original level or lost to the environment
in a form not useable to organisms (usually
heat)
2. Ecologists use models to trace this flow through ecosystems
A. Food Chain = Is A Simple Model That Scientists Use To Show
How Matter And Energy Move Through An Ecosystem.
i. Food Chains Can Consist Of Three Links, But Most
Have No More Than Five Links.
ii. Links In The Chain Are Represented By Trophic
Levels (feeding levels)
a. each organism in a food chain represents
one feeding step or trophic level
-producers are the first trophic level
-first order consumers eat producer and they
are the second trophic level
-second order consumer eat first order
consumers and they are the third trophic level
- and so on
iii. always start with a producer
iv. drawn using arrows that indicate the direction energy
moves
B. Food Webs = Model Created To Express All The Possible
Feeding Relationships At Each Trophic Level In A
Community.
i. more accurate representations of what really occurs
in nature
ii. organisms feed on more than one type of food
iii. different organisms eat the same type of food
C. Ecological Pyramids = Models Used To Depict Energy
Conversions In An Ecosystem.
i. shows the distribution of matter and energy within
an ecosystem
ii. the base of these pyramids are always producers
iii. higher trophic levels are layered on top of each
other
iv. three basic types
a. Pyramid of Energy
-each level in this pyramid represents the
energy available within that trophic level
-remember only 10% of the energy is available
for the next trophic level
-so the amount of energy decreases at each level
as you go up
b. Pyramid of Numbers
-each level in this pyramid represents the number of
organisms consumed by the levels above it
-shows that population size decreases at each
higher trophic level
-there are more producers, less 1st order consumers,
less 2nd order consumers and so on
c. Pyramid of Biomass
-biomass is the total weight of living matter
-each level in this pyramid represents the biomass of
each trophic level
-producers have the largest, and it decreases at each
higher level
3. Cycling Maintains Homeostasis
A. Matter and Energy are constantly recycled in the
universe
i. conservation of mass/energy
ii. The Carbon Cycle
a. carbon atoms make up many of the biological
molecules in living things
b. carbon is cycled through the environment from the
carbon dioxide in the atmosphere to usable
carbohydrates during photosynthesis, then organisms
release carbon dioxide back into the atmosphere
iii. The Nitrogen Cycle
a. nitrogen is converted from unusable atmospheric
forms into forms needed for life by lightning and
bacteria then back to atmospheric forms by bacteria
iv. Other elements such as calcium, sulfur and phosphorus
are also cycled through the environment
B. Some natural cycles
i. The Water Cycle
a. water is constantly moving between the
atmosphere and the earth
b. five key steps
-evaporation
- respiration
- transpiration
-condensation
-precipitation
2. Close Relationship For Survival
A. Symbiosis = Organisms Living Together.
i. a relationship in which there is a close and
permanent association between organisms of different
species
ii. three main types
a. Commensalism = Is A Symbiotic Relationship In Which One
Species Benefits While The Other Is Neither Harmed Nor
Benefited.
-ex. Spanish moss, orchids
b. Mutualism = A Symbiotic Relationship In Which Both Species
Benefit.
-ex. Ants and the Acacia Tree, sharks and cleaner fish
c. Parasitism =A Symbiotic Relationship In Which One
Organism Derives Benefit At The Expense Of The Other.
-ex. Fleas, tics, intestinal worms and their hosts (us or other animals)
-parasites do not want to kill their hosts, they depend on them
and if they die the parasite will die or have to find a new host
-Changing with the Environment
1. General
A. Ecosystems are always changing
B. Changes affect the communities within the ecosystem
C. There are patterns in these changes that explain how
the ecosystems have developed
2. Limiting Factors
A. Any biotic or abiotic environmental factors that
restrict the existence, numbers, reproduction or
distribution of organisms
B. Factors that affect an organisms ability to survive
in its environment
C. Examples: Food availability and temperature
D. These factors may limit one population, but the
affect on one population in a community can affect
others
-Succession: A Change in Communities over Time
1. General
A. Orderly, natural changes that take place in
communities of an ecosystem are referred to as
succession
B. Can be hard to observe as they can take place over
long periods of time
C. 2 types; primary and secondary
2. Primary Succession
A. The colonization of barren land by communities of
organisms
B. Takes place on land where there is no living
organisms (new land)
i. lava is the major cause
C. After some time primary succession slows down and
the community becomes fairly stable
D. Pioneer species are the first organisms to inhabit the
new area (small organisms)
i. ex. lichen
E. The community of organisms gradually changes and
adds new and bigger organisms
F. A stable mature community that undergoes little or
no succession is called a climax community
3. Secondary Succession
A. The sequence of community changes that takes
place when a natural disaster or humans actions have
disrupted an existing community
i. takes place on land where there was already
a community that has been disturbed
B. The community of organisms gradually changes
like in primary succession
C. Pioneer species are different than in primary
succession because soil already exists and bigger
species can start
D. Takes less time to reach climax than primary
succession because you it is not starting from scratch
E. see figure 3.3, page 68
Biomes
1. a biome is a large group of ecosystems that share the same
type of climax community
2. There are 2 basics types of biomes; aquatic and terrestrial
Challenges in:
1. Aquatic Biomes
A. In deep water, there are 4 general limiting factors
that decrease the population density as you go deeper
i. temperature drops as you go deeper
ii. less light penetrates as you go deeper
iii. oxygen availability decreases as you go
deeper
iv. pressure increases as you go deeper
B. approximately 75% of earth's surface is covered
with water
Challenges in:
1. Terrestrial Biomes
A. Support against gravity
B. Prevent water loss
2. Marine
A. Saltwater (most of the water on earth)
B. Oceans, seas and even some lakes
C. Contains the largest amount of biomass, living
material, of any biome on Earth
i. Most of this biomass is made up of very small
organisms called plankton
ii. Plankton form the base of most aquatic food
chains
D. Contains 2 zones
i. Photic - shallow portion that light penetrates
ii. Aphotic - deeper portion that light cannot
penetrate
3. Estuary
A. Where rivers (fresh water) join oceans (saltwater)
B. Fresh and salt water mix
C. Salinity can be anywhere from as salty as the ocean or
as saltless as fresh water
i. depends on how much fresh water the river
brings into the estuary
ii. varies with the tides
D. a wide variety of organisms can live here
E. Contain Salt Marsh ecosystem
i. Dominated by grasses
ii. Provide an abundant supply of food and shelter
4. Intertidal Zone
A. The portion of the shoreline between high and low tide
B. Tides vary depending on the season & moon phases
C. Contains sandy beaches and rocky shoreline
D. Productivity is limited due to waves crashing
E. Has high levels of sunlight, nutrients, and oxygen
F. Can include tide pools
G. Snails, starfish, mussels, barnacles, etc
5. Freshwater
A. No salt
B. Fish, algae, protists, mosquito larvae, tadpoles,
crayfish, etc
C. Lakes, ponds, streams, rivers, etc
6. Other aquatic biomes
A. places where land and water meet are called
wetlands
i. marshes - no trees, flowing water
ii. swamps - trees, flowing water
iii. bogs - no flowing water
Terrestrial Biomes
1. Land biomes
A. Latitude and climate
i. latitude describes your position in degrees
north or south of the equator
a. the sun strikes the earth differently at
different latitudes resulting in climate
differences
ii. climate is the wind, cloud cover,
temperature, humidity, and precipitation in an
area
iii. they are abiotic factors and they create
different biomes
2. Tundra
A. Circles the north pole
B. Treeless
C. Temperatures never rise above freezing for very long
D. Permafrost is under the topsoil
E. Even the topsoil is frozen most of the time
F. Topsoil is usually so thin that it can support only
shallow-rooted grasses and other small plants
G. The soil is also lacking in nutrients
i. The decay process is slow due to the cold
temperatures, so nutrients aren't recycled quickly
H. The growing season is short
i. This is a limiting factor also
I. Mosquitoes and other biting insects are common in the
short summers
J. Lemmings, weasels, arctic foxes, snowshoe hares,
snowy owls, hawks, musk-oxen, caribou, and reindeer
3. Taiga
A. Circles the tundra, just to the south
B. Northern coniferous forest, the dominant climax plants
are primarily fir and spruce trees. The topsoil is acidic and
poor in minerals (due to the evergreen needles)
C. The border between this and the tundra can be
indistinct
D. Usually warmer and wetter than the tundra, but the
prevailing climate is still harsh with long severe winter and
short mild summers. Permafrost is usually absent
E. Stretches across much of Canada, Northern Europe,
and Asia
F. During secondary succession, the first trees to colonize
may be birch, aspen, or other deciduous species
G. More large species of animal are found here
i. The larger trees provide more food and shelter
for them than in the tundra
ii. Snowshoe hare, Lynx, Caribou, Moose
4. Desert
A. The driest of the biomes
B. South of the taiga
C. Sparse to almost nonexistent plant life
D. Usually gets less than 25cm of precipitation
annually
E. Atacama desert in Chile is the driest place in the
world with an annual rainfall of 0cm
F. Lizards, tortoises, snakes
G. Plants vary depending on the amount of rainfall in an
area
i. Creosote bushes, mesquite trees, cacti, and
sometimes almost no plant life
ii. Various adaptations to deal with the arid climate
1. some are annuals that germinate from seed
to maturity quickly after a sporadic rain
2. photosynthetic stems
3. a thick waxy coat that reduces water loss
4. some have leaves that curl up or drop of to
reduce water loss
5. some have spines, thorns or poison that
discourage herbivores from eating them
H. Most desert mammals are small herbivores that remain
under cover during the heat of the day
i. Kangaroo rat (doesn't drink water), pronghorn
antelope, foxes, scorpions, coyotes, hawks, owls, road
runners
5. Grasslands
A. 25-75cm of precipitation annually
B. usually experience dry seasons and therefore have
insufficient water to support forests
C. This biome occupies more area than any other land
biome
D. Has higher biodiversity than desert
E. The soil has considerable humus content
F. Ideal for growing cereal grains (oats, rye, wheat)
G. Summers are hot, winters are cold, and rainfall is
uncertain
H. Prairies, steppes, savanna, and pampas are other
names for it
I. Populated by large herd animals
6. Temperate Forests
A. Usually 70-150cm of precipitation annually
B. Top soil is rich in humus, a deeper layer of clay
C. Even amount of precipitation for the 4 seasons
D. Also called deciduous forest
E. Typical trees: birch, hickory, oak, beech, and maple
F. Squirrels, mice, rabbits, deer, bears, many birds, etc.
G. Where we live
7. Tropical Rain Forests
A. The most biologically diverse biome
B. Warm and wet
C. Equatorial Regions
D. At least 200cm of rain annually
E. High humidity
F. Tree roots are often shallow
G. Most nutrients are tied up in living material, so the
soil is not nutrient rich (the nutrients are used up fast)
H. 3 layers in the rainforest
i. the canopy; tops of the trees
ii. the understory; the area between the ground
and the tree tops
iii. the ground; the moist forest floor
Section 1: Population Dynamics
*Principles of Population Growth
1. General
A. Populations are groups of organisms of the same
specie
B. Population growth is the change in the size of a
population with time
C. Scientists have found clear patterns of how and
why populations grow
2. How fast do populations grow
A. Populations do not grow in a linear fashion
B. Populations grow in an exponential fashion
i. The initial increase in # is slow due to the
small # of organisms able to reproduce, then
the rate increases rapidly as the total # of
organisms potentially reproductive organisms
increases
ii. Exponential growth occurs when the # of
organisms increases by an ever increasing rate,
this results in a population explosion
iii. This results in a J shaped curve, see fig. 5.3
on page 115
3.
Limits of the environment
A. Populations cannot grow indefinitely
B. Population size does have a limit
C. Populations do have limiting factors in their
environment. These limiting factors slow the growth of a
population.
i. Ex. Food availability and space
C. This leveling off of population growth results in an s
shaped curve
i. See fig. 5.4 page 118
ii. There is a plateau when the # of organisms the
environment can support is reached
D. The # of organisms of a population that a particular
environment can support over a period of time is known as its
carrying capacity
i. Often represented by the letter K
E. When populations are under the carrying capacity, births
will exceed deaths
F. If the population overshoots the carrying capacity, deaths
will exceed births until populations are once again at carrying
capacity
*Reproductive Patterns
1. In nature, some populations remain in equilibrium (a state
of rest or balance), some do not
A. This occurs because there are 2 basic growth
patterns, called life history patterns, that populations
can follow
i. Some populations reproduce very rapidly
and produce many offspring
1. Ex. mosquitoes
ii. Some populations have a slow rate of
reproduction with few young
1. Ex. elephants
iii. Which type a specie uses depends mainly on
environmental factors
B. Species in an unpredictable and rapidly changing
environment survive better with a rapid life history pattern
i. These organisms usually have similar adaptations
1. Ex. Small body size, mature rapidly,
reproduce early, & have short life span, many young
ii. Ex. Mosquitoes
iii. Populations of these organisms increase and decrease
rapidly as their environment changes
1. The small surviving population will begin
reproducing exponentially when conditions are
favorable again
C. Species that live in a more stable environment usually have a
slow rate life history pattern
i. Ex. Elephants
ii. Are usually large in size, long lived, produce few
young and mature slowly
iii. These organisms usually maintain populations
near the carrying capacity
D. Theoretically, any population could follow either strategy
depending on environmental conditions
a. Ex. In the pioneer stage of succession, there is no
crowding, and rapid population growth seems to be
affective
E. Environmental limits to population growth
a. Limiting factors regulate the size of a population
b. Ecologists have recognized 2 types of limiting factors
i. Density-dependent factors have an increasing
effect on a population as the population increases
in size
1. Ex. Disease, parasites, competition
ii. Density-independent factors affect all
populations regardless of their density
1. Usually abiotic factors
2. Ex. Temperature, storms, drought etc.
*Interactions among organisms that limit population size
1. Populations are also controlled by various interactions
among organisms within the community
2. Predation affects on population size
A. Predation is necessary in a community, it ensures
the continuation of the flow of energy throughout the
ecosystem
B. It also may be a limiting factor on a prey
population size
C. Most prey populations are controlled in some way
by predators
D. Populations of predators and prey change over years,
many in a cyclical fashion
i. See fig. 5.8 on page 122
ii. Usually with the populations increasing and
decreasing at the same times
E. Predators help to weed out the sick, old, young and week
i. This leaves the strong and well adapted left to
reproduce
3. The effects of competition
A. Organisms within a population compete for
resources
B. When population is low, resources are abundant
C. As population increases the competition for
resource increases
D. Density-dependent factor
E. When the population becomes to big and the
demand for the resources is greater than the supply of
resources, the population size decreases
4. The effects of overcrowding and stress
A. When populations become crowded, individuals
may exhibit stress
B. Symptoms of stress from overcrowding include
aggression, decrease in parental care, decreased
fertility, and decreased resistance to disease
C. All of these symptoms can lead to a decrease in
population size (which relieves the overcrowding)
Section 2: Human Population
*World Population
1. General
A. Demography is the study of human population
size, density and distribution, movement and
birth/death rates
2. Human Population Growth
A. humans consciously change their environment,
so human population is different than other
populations
B. humans have reduced or eliminated many of
their limiting factors which have allowed the
human population to grow
i. medical advances
ii. agriculture advances
iii. eliminate competition
3. Calculating growth rate
A. 4 factors affect human population growth
i. birth rate
ii. death rate
iii. immigration - movement into a population
iv. emigration - movement out of a population
B. to calculate population growth rate we must take all of
these factors into account
i. (birth rate + immigration) - (death rate +
emigration ) = population growth rate
ii. this just tells how many new individual are in a
population
iii. if the PGR is positive it means more individuals
are entering the population than leaving it, if the
PGR is zero it means that individuals are entering
and leaving the population at the same rat, and if
the PGR is negative it means that more individuals
are leaving the population than entering it
4. The effect of a positive population growth rate
A. unless the growth rate becomes negative, a popula
tion is still growing
i. ex. In 1995 the world PGR was 1.7% and in
2001 it dropped to 1.3%
ii. therefore, the population was still growing
but at a slower rate
5. Doubling time
A. the time needed for a population to double in size
B. a country with a slow doubling time is considered a
developed country, while a country with a rapid
doubling time is considered a developing country
6. Age Structure
A. refers to the proportions of the population that are
in different age levels
B. shows the proportions of males and females in each
age group and those within child bearing age and
elderly (can help us predict trends in birthrates and
deathrates)
C. if the percentage of people in each age category is
fairly equal the population is considered stable,
rapidly growing populations have higher numbers in
lower age groups (more people in child bearing age)
D. see figure 4.11, page 103