Transcript Ecology - Toolbox Pro

Ecology
• Ecology is the study of the interactions among
organisms and their interrelationships with the
physical environment. All living organisms are
dependent upon other living things as well as
dependent on the nonliving environment.
• Habitat – the place where an animal or plant
lives.
• Niche – the role an organism fits into within its
ecosystem.
Organization
Ecosystems
• The ecosystem is the structural and functional unit
studied in ecology. It is the lowest level of organization in
ecology in which all living and nonliving environmental
factors exist and interact.
ECOSYSTEM STRUCTURE AND FUNCTION:
An ecosystem involves interactions between abiotic
(nonliving) and biotic (living) factors. An ecological
system is a self-sustaining unit if the following
requirements are met:
 It must have a constant source of energy and a living
system capable of incorporating this energy into organic
compounds.
 It must have mechanisms to cycle and recycle materials
between the organism and their environment.
Terrarium: Balanced Ecosystem
Carrying capacity – the largest population
of any single species that an area can
support.
Components of an Ecosystem
ABIOTIC FACTORS:
The abiotic environment includes physical and chemical
factors which affect the ability of organisms to live and
reproduce.
The abiotic factors include:
• Intensity of light
• Range of temperatures
• Amount of moisture
• Type of substratum (soil)
• Availability of inorganic substances such as minerals
• Supply of gases such as O2, CO2, N2
• pH
Limiting Factors
Each of these factors varies in the environment and, as such, may act
as a limiting factor, determining the types of organisms which may
exist in that environment. Examples of limiting factors include:
•
•
•
•
•
Some plants live well on a forest floor under tall trees, but would not do well
in an open field due to the increased intensity of light.
At low annual temperatures common to the northern latitudes determines in
part what species of plants can exist in that area because enzymes of
different species work best at different temperatures.
The amount of oxygen dissolved in a body of water will help determine
which species of fish will exist there. Fish that need high oxygen levels
would suffocate and die with a severe drop in the oxygen level in the water.
The salt-laden air and water of coastal areas limit what species can exist in
those regions. Some species of fish, shellfish, and other marine species
would die in freshwater due to an imbalance of water pressure in their
tissues.
More than 200 lakes in the Adirondacks have virtually no life in them
because of low pH caused by acid rain.
Biotic Factors
Biotic factors are all the living things that
directly, or indirectly, affect the
environment. Thus, the organisms, their
presence, parts, interaction, and wastes,
all act as biotic factors. Biotic factors
interact in many ways such as in
nutritional relationships and symbiotic
relationships.
Nutritional Relationships:
Nutritional relationships involve the transfer of nutrients from one
organism to another within an ecosytem
• Autotrophs- Organisms who can synthesize their
own food (organic nutrients such as
carbohydrates, proteins, lipids and nucleic acids)
from inorganic compounds and a usable energy
source.
• Heterotrophs- Organisms who cannot synthesize
their own food and are dependant upon other
organisms for food
• Saprophytes- Heterotrophic (nongreen) plants,
fungi, and bacteria which live on dead matter
and recycle materials in the environment. Ex:
mushrooms, breadmold and bacteria of decay
• Herbivores- Animals which consume
plants. Include the “grazing” animals such
as cows, rabbits and deer.
• Carnivores- Animals which consume other
animals. Include: predators which kill and
consume prey (wolves & eagles); and
scavengers who feed on animals they
have not killed (buzzards and crabs.)
• Omnivores- Animals that consume both
plants and animals. Ex: humans
Symbiotic Relationships
Different organisms live together in a close
association which may include: nutritional,
reproductive, and protective relationships.
This living together in close association is
known as symbiosis. Symbiotic
relationships may or may not be beneficial
to the organisms involved. Types of
symbiosis include:
• Commensalism- One organism is benefited and the
other is not adversely affected (+,0). Ex: barnacles on
whales and orchids & bromeliads on large tropical trees.
• Mutualism- Both organisms benefit (+, +). Ex: nitrogenfixing bacteria within the nodules of legumes, certain
protozoa within termites, and a flower and bee.
• Parasitism- The parasite benefits at the expense of the
host (+, -). Ex: athlete’s foot fungus on humans and
tapeworm, heartworm, and fleas in dogs.
Energy Flow Relationships
If an ecosystem is to be self-sustaining it must contain a
constant supply of energy which is available to all the
organisms within the ecosystem. The energy must flow
from organism to organism.
ENERGY FLOW
Those life activities which are characteristic of living
organisms require the expenditure of energy. The
pathways of energy through the living components of an
ecosystem are represented by food chains and food
webs.
Green plants convert radiant energy from the Sun into
chemical energy (food). A food chain involves the
transfer of energy from green plants through a series of
organisms with repeated stages of eating and being
eaten. Ex: Grass→Grasshopper→Frog→Snake
Food Chain
FOOD WEB. In a natural
community, the flow of energy
and materials is much more
complicated than is illustrated by
one food chain. Since practically
all organisms may be consumed
by more than one species, many
interactions occur among the food
chains of any community. These
interactions are described as a
food web. Interactions in a food
web involve:
Food Web
• Producers- The energy for a community is
derived from the organic compounds
synthesized by green plants. Autotrophs are the
primary producers in all ecosystems.
• Consumers- Herbivores are primary consumers.
Carnivores are secondary consumers.
Omnivores may be either primary or secondary
consumers.
• Decomposers- Organic wastes and dead
organisms are broken down to simpler
substances, where chemical substances are
returned to the environment where they can be
used by other living organisms.
Pyramid of Energy
There must be much more energy at the producer level in a
food web then at the consumer levels. In turn, there is
more energy at the primary consumer level than at the
secondary consumer level. A pyramid of energy can be
used to illustrate the loss of usable energy at each
feeding level. Each consumer level of the food pyramid
utilizes approximately 10% of its ingested nutrients to
build new tissue. This new tissue represents the food for
the next feeding level. The remaining energy is lost in
the form of heat and unavailable chemical energy.
Eventually, the energy in an ecosystem is lost and is
radiated from the Earth’s system. Thus, an ecosystem
cannot sustain itself without the constant input of energy
from the Sun.
Biomass pyramid
• In general, the decrease of energy at each successive
feeding level means that less biomass (amount of
organic matter) can be supported at each level. Thus,
the total mass of carnivores in a particular ecosystem is
less than the total mass of producers.
• For example, if the population of rabbits in a community
decreases, there is less food available for the foxes. This
will cause a decrease in the number of foxes born as
there is too little food to support a larger population. With
fewer foxes, the rabbit population has a chance to
increase. The biomass relationship is a good example of
the balance in nature, the homeostasis of an ecosystem.
Prairie Ecosystem
Energy Pyramid Relationships
bacteria
Prairie
Material Cycles
• In a self-sustaining
ecosystem, material
must be cycled
among organisms
and the abiotic
environment. Thus,
the same materials
can be reused by
different living
organisms.
Carbon-Hydrogen-Oxygen Cycle
Water &
& Water
• The carbon-hydrogenoxygen cycle involves the
processes of respiration
and photosynthesis. In
respiration, oxygen and
glucose are combined
releasing energy and
producing water and
carbon dioxide. In
photosynthesis, water and
carbon dioxide with energy
from the Sun are combined
to produce glucose
(containing the energy) and
oxygen. Each process
compliments the other, and
the ecosystem maintains its
balanced communities.
Water Cycle
• Water is vital to all living
organisms and is a
primary limiting factor
within any ecosystem.
The water cycle involves
the processes of
photosynthesis,
transpiration,
evaporation,
condensation,
respiration, and
excretion.
Photosynthesis
Nitrogen Cycle
The nitrogen cycle “cycles” nitrogen necessary for the production of
proteins, essential to all living things. It is an example of a material
cycle involving decomposers and other soil bacteria which, in part,
break down and convert nitrogenous wastes and the remains of
dead organisms into materials usable by autotrophs.
The essential parts of the nitrogen cycle include:
 1.Atmospheric nitrogen is converted into nitrates by nitrogen-fixing
bacteria.
• Plants use nitrates for protein synthesis.
• Animals which eat plants convert the plant protein into animal
protein.
 2.Nitrogenous wastes and the bodies of dead plants and animals
are broken down by decomposers (bacterial decomposition) and
ammonia is released.
 3.Ammonia may be converted into nitrates by nitrifying bacteria.
 4.Nitrogen containing compounds may also be broken down by
denitrifying bacteria, resulting in the release of nitrogen into the
atmosphere.
Atmospheric free nitrogen
Animal waste &
dead plants
Nitrogenfixing
bacteria in
soil
Denitrification
Decay Bacteria
Nitrifying
Bacteria
ammonia
Nitrates
Used by plants
Denitrifying
bacteria
Ecosystem Formation
Ecosystems tend to go through dynamic change with time
until a stable system (climax community in a state of
equilibrium is attained. The type of ecosystem that is
formed depends on the climate limitations of a particular
geographical area.
SUCCESSION
The replacement of one community by another until a
stable stage (climax community) is reached is called
ecological succession.
Succession may be said to begin with pioneer organisms,
since these are the first living things to populate a given
location. For example, lichens (a symbiotic association
between fungus-alga) are the pioneer organisms on bare
rock. Pioneer organisms modify their environment.
Seasonal die-back and erosion, for example, would
create pockets of “soil” in the crevices in bare rock.
Changes in Succession
Each community modifies the environment, often making it
more unfavorable for itself, and apparently, more
favorable for the following community which infiltrates
the first community over a period of years. For example,
as lichens grow and reproduce, they add organic matter
and moisture to their substratum. After a period of time,
humus is made and is too rich and moist for the lichen to
survive. The lichens die but produce a richer substratum
that will support seeds for the development of grasses
and herbs, the next stage of succession. A typical
successional sequence in New York State might be:
lichen (pioneer), grass, shrub, conifer, and deciduous
woodland (climax).
Lichens
&
annuals
Perennials
& Grasses
Shrubs
Conifers: pines &
firs (softwoods)
Deciduous trees:
maples, oaks, and
beeches
(hardwoods)
• Plant species (flora) dominate in the sense that they are
the most abundant food sources. Plant succession is a
major limiting factor for animal (fauna) succession.
Communities are composed of populations able to exist
under the prevailing conditions and are identified by their
own dominant plant species – the one that exerts the
most influence over the other species present. Ex. a
Sphagnum Bog
• A climax community is a self-perpetuating community in
which populations remain stable and exist in balance
with each other and the environment. The oak-hickory
and the hemlock-beech-maple associations represent
two climax communities found in New York State.
• A climax community continues until a catastrophe or a
change in a major biotic or abiotic factor alters or
destroys it, thus producing “nonclimax” conditions.
Some examples of natural and man-caused factors that
affect a climax community include:
 Forest fires
 Abandoned farmlands
 Areas where topsoil has been removed
• Thereafter, succession once again occurs leading to
another climax community. The original climax
community may be reestablished or a new climax
community may be established if the abiotic environment
has been permanently altered.
• Competition occurs when different species or organisms
living in the same environmet (habitat) utilize the same
limited resources, such as food, space, water, light,
oxygen, and minerals. The more similar the requirement
of the organisms involved, the more intense the
competition. This competition between different species
is called interspecies competition.
Biomes
• The term biome refers to the most common climax
ecosystem that will form in geographic regions of similar
climatic conditions. Biomes are terrestrial or aquatic. The
temperate deciduous forest of the U.S. is a terrestrial
biome. The ocean is an aquatic biome.
Terrestrial Biomes
• The major plant and animal associations on land are
determined by the major climatic zones of the world,
which are modified by local land and water conditions.
Climates will vary as to temperature, solar radiation, and
precipitation. The presence or absence of water is a
major limiting factor for terrestrial biomes.
Characteristics:
• Land biomes are characterized and sometimes named by the climax
vegetation in the region. The major land biomes, and their
characteristic flora, and fauna are listed in the following chart.
CHARACTERISTICS
BIOME
CLIMAX FLORA
CLIMAX FAUNA
Tundra
Lichens, mosses,
grasses
Caribou, snowy
owl
Taiga
conifers
Moose, black bear
Long, severe winters,
summers with thawing
subsoil
TemperateDeciduous
Forest
Trees that shed
leaves (deciduous
trees)
Grey squirrel, fox,
deer
Moderate precipitation,
cold winters, warm
summers
Tropical Rain
Forest
Many species of
broad-leaved plants
Snake, monkey,
leopard
Heavy rainfall, constant
warmth
Grassland
grasses
Pronghorn
antelope, prairie
dog, bison
Rainfall & temperature
vary greatly, strong
prevailing winds
Desert
Drought-resistant
shrubs and
succulent plants
Kangaroo rat,
lizard
Permanently frozen
subsoil (permafrost)
Sparse rainfall, extreme
daily temperature
changes
altitude
low
• Climatic
conditions change
with latitude and
altitude. Earth
latitude and
altitude are similar
in that as both
increase, the
limiting factors
change in a
similar manner,
and the
organisms
change as well.
high
Geographic
Factors:
low
latitude
high
Fresh Water Biomes:
The fresh water biome includes ponds, lakes, and rivers.
The areas which make up a fresh water biome show
considerable variation in:
• Size
• Current velocity
• Temperature
• Concentration of dissolved gases
• Suspended particles
• Rate of succession
Ponds and small lakes, for example, fill in due to the
seasonal die-back of aquatic vegetation and the erosion
of their banks. Eventually a small body of water enters
into terrestrial succession terminating in a terrestrial
climax community.
Marine Biomes
The oceans of the world are a
continuous body of water that
• Provides the most stable
aquatic environment
• Absorbs and holds large
quantities of solar heat and
helps to stabilize the Earth’s
atmosphere
• Contains a relatively constant
supply of nutrient materials
and dissolved salts
• Serves as a habitat for a large
number of diverse organisms
A great amount of food production
in the world occurs in the
oceans along the edges of the
land masses (coastal waters),
the deeper regions being too
dark.
Biodiversity
• Biodiversity is a measurement of the degree to which
species vary within an ecosystem. There is a strong
connection between biodiversity and the stability of an
ecosystem.
• The interactions between organisms may allow an
ecosystem to remain stable for hundreds or thousands of
years. Populations tend to fluctuate in predictable
patterns. Loss of biodiversity upsets this stability. For
example, when the prey population increases, a large
food supply causes the size of the predator population to
rise. Because each predator requires many prey to meet
its energy needs, the prey population rapidly decreases.
Soon, with the decline in a prey population, some of the
predators begin to starve. When only a few predators
remain alive, the prey population reproduces and greater
numbers of prey survive. The cycle begins anew.
• Ecosystem instability not only
affects plants and animals, but
also humans. For example, a
natural forest contains many
different species of trees. If
disease or insects attack one
population, nearby trees of
another species are likely to
survive. As opposed to a tree
farm, where all of the trees
planted are of a single species
that could be seriously
damaged by a single disease
or insect attack. Entire crops
may be lost from any
disruption in an ecosystem.
• Furthermore, biodiversity
ensures a rich variety of
genetic material for medicine,
insecticides, and other useful
resources.
Biosphere
and
Humans
Humans exercise a unique and powerful influence on the physical and living
world and have modified their environment more than any other living
thing.
Renewable resources:
• Although many resources are renewable, they must used carefully.
Increased consumption can stress the natural processes that renew some
resources. As a result, the resource might be unable to renew itself. For
example, commercial fishing can stress certain fish populations.
Nonrenewable resources:
• Our increasing consumption of resources that cannot be replaced naturally
is becoming a serious problem. Most metals, such as the aluminum we
use for packaging, and other minerals, such as silicon we use for
computer chips, are nonrenewable resources. Fossil fuels, such as the
gas that runs our cars and the coal that powers many factories, are also
nonrenewable resources.
Population growth:
• Most species in new environments can have a
period of rapid population growth. The
population increase will eventually level off as it
approaches the ecosystem’s carrying capacity,
which is the number of individuals the
environment can support.
Human Population Growth:
• The total population of humans has risen at a
rapid rate, partly because of the removal of
natural checks on the population, such as
disease. This continued increase in the human
population has far exceeded the food producing
capacities of many ecosystems in the world. The
change in the world population is illustrated in
the population graph below.
The Plague
•
A population growth curve:
In new environment, the
population usually increases
quickly, but it stablilizes
when it reaches the carrying
capacity of that environment.
Growth curve for the human
population worldwide
Negative Aspects
Disruptions that humans cause to the natural systems
directly affect at least one of the components of an
ecosystem and this, in turn, affects the remaining
components.
Human Activities:
Some activities have led to the extinction or endangerment
of numerous species of plants and animals as well as
producing less favorable living conditions for many
species, including humans.
• Overhunting- many species have gone extinct. Ex: Dodo
bird, Wooly Mammoth. Many countries still hunt whales,
sharks, etc.
• Importation of organisms- Non-native
species disrupt stable ecosystems. Ex:
Japanese beetle, Gypsy moth, Purple
loosestrife, Hogweed, Zebra Mussels,
Dutch elm disease.
• Australia – Cane Toad
Imported Organisms
Zebra
Mussels
Purple
Loosestrife
Hogweed
• Exploitation- elephants and walruses killed
for tusks, exotic birds endangered due to
pets, rainforests depleted for plywood.
• Poor land use management- urbanization disrupts
natural habitats, agricultural land, and watersheds.
• Water pollution- heat, sewage, and chemicals such as
phosphates, heavy metals and PCB’s cause serious
health problems and destroy life forms.
• Air pollution- Nitrogen oxides and sulfur dioxide combine
with water to form acid rain-kills living things and
destroys buildings.
• Biocide use- pesticides and insecticides contaminate
soil, atmosphere, water supply and disrupt food webs.
Ex: DDT
• Disposal problems- human supplies accumulate solid,
chemical, and nuclear waste. Nuclear plants produce
permanent dangerous radioactive wastes.
• Ozone depletion- the
release of certain
industrial gases
(CFC’s) into the
atmosphere has led to
destruction of much of
the ozone shield, the
layer of ozone gas in
the upper atmosphere
that protects Earth
from some of sun’s
radiation.
• Global Warmingatmospheric gases,
called greenhouse
gases, trap and
absorb the infrared
radiation that bounces
off Earth’s warmed
surface. Recently,
greenhouse gases
have increased,
raising the Earth’s
average temperature.
Positive aspects:
• Population control- family planning has become
accepted by much of the world to conserve limited
resources.
• Conservation of resources- reforestation and
covercropping protect land, water, and energy
conservations improve, as well as recycling.
• Pollution controls- laws and new techniques
of sanitation or the disposal of industrial
hazardous materials have improved land,
water and air quality. Why the Eagles Returned (11 min)
• Species preservation- wildlife refuges,
national parks, game laws, fisheries and
endangered species protection have
improved.
• Biological control- encourages food webs
and ecosystems by decreasing the use of
pesticides. Ex: Japanese beetle traps,
ladybugs for aphids.
In recent years, new and tougher laws which
regulate and guide the use of natural
habitats have been enacted throughout the
country. For example, the Freshwater
Wetlands Act.