Download Chapter 5: Interactions: Environments and Organisms

Chapter 5: Interactions: Environments and Organisms
Ecological Concepts (Figure 5.1)
 Ecology: The study of ways of organisms interacts with each other and with their
surroundings.
 Environment: Everything that affects and organism during its lifetime is collectively known
as its environment, which contains abiotic (nonliving) and biotic (living) factors.
 Abiotic Factors: Nonliving things that influence an organism, including energy,
nonliving matter, living space, and process that involves the interactions of
nonliving matter and energy.
 Energy: Required by all organisms to maintain themselves.
Ultimate source: Sun.
Plants: Directly use sun by photosynthesis of sugar.
Animals: Obtain energy by eating plant.
 Matter: Provide the structural framework of organisms, which obtain these
materials from environment.
 Atoms: In form of matter, which become part of an organism’s body
structure for a short period and eventually all of them are returned to the
environment through respiration, excretion, or death and decay.
 Space: The place organisms inhabit that has a particular structure and
location. Ex. Ocean, mountains, near equator area, near poles area.
 Ecological processes: Involving interaction between matter and energy. Ex.
Solar radiation affects ocean currents, generates wind and climate change,
evaporation of water into atmosphere and fall as precipitation.
 Biotic Factors: Include all forms of life with which it interacts.
Ex.
Plants: photosynthesis
Animals: eat other organisms
Bacteria and fungi: cause decay
Bacteria, viruses, parasitic organisms: cause disease
 Limiting Factors: A shortage or absence of a factor can restrict the success of the species is
known as a limiting factor, which may be abiotic or biotic and can be quite different form
one species to the other species.
Ex.
Plants: scarcity of water, light or specific soil nutrients.
Animals: climate or availability of a specific food.
Aquatic Species: cool oxygenated water.
 Range of Tolerance: each species has its own.
Ex. Trout: unable to survive in low [O2] and high temperature.
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Habitat and Niche
 Habitat: The place an organism lives
Ex. Moss: cool, moist and shady.
 Niche: The functional role an organism has in its surroundings.
Ex. Beaver: building dam providing deep water for protection and habitat for ducks and
fish, flooding area, killing trees, become victim when animal attracts to pond, eating
suitable woody trees. When foods are gone, they migrate to other area along the stream.
The Role of Natural Selection and Evolution
 General rule: Organisms are well adapted to their surroundings and fill a particular niche.
What leads to this high adaptation?
 Genes: The distinct pieces of DNA that determines the characteristics an individual
displays.
 Population: Organisms of the same kind found within a specific geographic region.
Individuals will have very similar sets of genes but there are some variations.
Genes are passed from one generation to the next by reproduction.
 Species: A population of all the organisms potentially capable of reproducing
naturally among themselves or interbreeding and having fertile offspring. (Fig. 5.8)
Usually requires specific conditions.
Ex. Horse-horse, donkey-donkey, horse-donkey (= mule, infertile)
Asexual reproduction:
1) Organisms produce copies of them without mating. (non-species)
2) Organisms produce copies of them by mating (species) and without mating
(non-species).
Natural Selection by Charles Darwin: The mechanism causes evolution to occur.
 Not understanding the concepts of genes but understanding characteristics were passed
from parents to offspring.
 Observed highly adaptive nature of the relationship between organisms and their
environment and developed the concept of natural selection to explain how this adaptation
came about.
 The process that determines which individuals within a species will reproduce and pass
their genes to the next generation.
 Evolution: The changes we seen in the genes and the characteristics displayed by
successive generations of a population of organisms over time.
 Steps involved:
1) Genetic Variation: Individuals within a species show genetically determined variation;
some of the variations are useful and other are not. (Ex. color variation: white, yellow,
black, red). (Fig. 5.10)
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2) Excessive Reproduction: Organisms within a species typically produce many more
offspring than are needed to replace the parents when they die. Most of the offspring die.
Ex. Blueberries, rabbits. (Fig. 5.11)
3) The excessive number of individuals results in a shortage of specific resources.
Ex. Individual species compete with each other for food, space, and mate that are in limited
supply.
4) Because of variation among individuals, some have a greater chance of obtaining needed
resources and, therefore, have a greater likelihood of surviving and reproducing than others.
Ex. Individuals that have genes that allow them to obtain needed resources and avoid
threats to their survival will be more likely to survive and reproduce.
5) As time passes and each generation is subjected to the same process of natural selection,
the percentage of individuals showing favorable variations will increase and those having
unfavorable variations will decrease.
Evolutionary Patterns
 Speciation:
1) The production of new species from previously existing species.
2) It is thought to occur as a result of a species dividing into two isolated subpopulations.
3) If two subpopulation contain some genetic differences and their environments are
somewhat different, natural selection will work on the two groups differently and they
wil begin to diverge from each other.
4) Eventually, the differences may be so great that the two subpopulations are not able to
interbreed. At this point, they are two different species. (Fig. 5.13)
5) For plants, polyploidy is another common mechanism results in new species. Polyploidy
is a condition in which the number of sets of chromosomes in the cells of the plant is
increased.
 Extinction:
1) The loss of an entire species and is a common feature of the evolution of organisms.
2) The environment in which organisms exist does not remain constant over long time
periods.
3) Those species lack the genetic resources to cope with a changing environment go
extinct.
4) Humans have had a significant impact on the extinction of many kinds of species.
 Coevolution:
1) The concept that two or more species of organisms can reciprocally influence the
evolution of other organisms.
Ex. Tubular flower (nectar at the base of flower) and hummingbird (with long bill)
Kinds of Organism Interactions
 Predation: A common interaction occurs when one organism, known as predator, kills and
eats another, known as the pray.
Ex. Lion and zebra, robin and earthworm, wolf and moose, etc.
A high reproductive rate is an adaptation common to many pray species.
 Competition: Two organisms strive to obtain the same limited resource.
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1) Intraspecific competition: Competition between members of the species.
Ex. Intraspecific competition for sunlight among pine trees results in the tall, straight
trunks. (Fig. 5.17)
2) Interspecific competition: Competition between members of different species.
Ex. Hawks, foxes, owls, and coyotes may compete the same prays.
 Competition and Natural Selection
1) The major force in shaping the evolution of a species is the competition among
members of the same species.
2) When resources are limited, the less well-adapted individuals are more likely to die or be
denied mating privileges.
3) Because of the most successful organisms are likely to have larger numbers of offspring,
each succeeding generation will contain more of the genetic characteristics that are
favorable for survival of the species in that particular environment.
Symbiotic Relationships
 Symbiosis: A close, long-lasting, physical relationship between two different species.
 Categories:
1) Parasitism: (Fig. 5.20)
 A relationship in which one organism, known as the parasite, lives in or on another
organism, known as host, from which it derives nourishment.
 Parasites, usually much smaller than the host, harm the host and gradually kills the
host.
o Ectoparasites: live on the surface of their hosts. Ex. Fleas, lice, etc.
o Endoparasites: live inside the bodies of their hosts. Ex. Tapeworm.
2) Commensalism:
 A relationship between organisms in which one organism benefits while the other
is not affected.
 It’s possible tovisualize a parasitic relationship evolving into a commensal one.
Ex. Shark and remora.
3) Mutualism: Another kind of symbiotic relationship and is actually beneficial to both
species involved.
 In many, the relationship is obligatory: one can not live without the other.
 In others, the species can exist separately but are more successful when they are
involved in the relationship.
Ex. Fungus and root association (i.e. mycorrhizae): fungi obtain nutrients like
PO43- and NO3- to make p and N available to plants.
Some Relationships are Difficult to Categorize
Ex. Nest (Brood) parasitism: (Fig. 5.23) Cowbirds and European cuckoos laid eggs in other
birds’ nests and let other birds to raise their young.
Community and Ecosystem Interactions
 Community: An assemblage of all the interacting populations of different species of
organisms in an area. Some plays minor roles, while others play major roles.
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 Ecosystem: A define space in which interactions take place between a community, with all
its complex interrelationship and the physical environment. The physical world has a
major impact on what kinds of plants and animals can live in an area.
 Major Roles of Organisms in Ecosystems
1) Producers: Organisms that able to use sources of energy to make complex, organic
molecules from simple inorganic substances in their environment.
Ex. Plants, algae, phytoplankton, etc.
2) Consumers: Organisms that require organic matters as a source of food to provide
themselves with energy and the organic molecules necessary to build their own
bodies.
 Primary consumers (i.e. herbivores): animals that eat producers as a source of
food. (Cows, horses, etc.)
 Secondary consumers (i.e. carnivores): animals that eat other animals. (Eagles,
lions, etc.)
 Omnivores: Animals that eat both plants and animals. (Foxes, bears, etc.)
 Decomposers: Organisms that use nonliving organic matter as a source of
energy and raw materials to build their bodies. (Bacteria, fungi, small
animals, etc.)
 Keystone species: One that has a critical role to play in the maintenance of specific
ecosystems. (Fig. 5.24)
Energy Flow through Ecosystem (Fig. 5.26)
 Ecosystem: 1) A stable, self-regulating unit via growing, reproducing, dying, and decaying.
2) Having a constant input of energy to retain its stability.
3) Sunlight: The only significant input of energy.
4) Producers trap the solar energy through photosynthesis to make it available to
the ecosystem.
5) Energy stored in the producers are transferred to other organisms when the
producers are eaten.
 Tropic Levels: Each level in the flow of energy through an ecosystem. (Fig. 5.25)
1) First tropic level: producers.
2) Second tropic level: herbivores.
3) Third tropic level: carnivores that eat herbivores.
4) Fourth tropic level: carnivores that eat other carnivores.
 Energy Relationships:
1) 2nd law of thermodynamics: When energy is converted from one form to another, some
of energy is converted to a non-useful form, typically low-quality heat, which is
dissipated to the surroundings and warms the air, water or soil.
2) The amount of energy contained in higher tropic levels is considerably less than that at
lower level, as it requires energy to chew, defend nests, or produce and raise offspring.
3) Ecologists use biomass (the weight of mass in a tropic level) to measure the amount of
energy contained in each tropic level.
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Food Chain and Food Web
 Food chain: A series of organisms occupying different tropic levels through which energy
passes as a result of one organism consuming another. (Fig. 5.27)
 Detritus: The small bits of nonliving organic material.
 Food web: When several food chains overlap and intersect. (Fig. 5.28)
Nutrient Cycles in Ecosystems----Biogeochemical Cycle
 Biogeochemical cycle: The nutrient cycle as all matter is made up of atoms and atoms are
cycled between the living and nonliving portions of ecosystem.
 Carbon Cycle ((Fig. 5.29): The processes and pathways involved in capturing inorganic
carbon-containing molecules, converting them into organic molecules that are used by
organisms, and the ultimate release of inorganic carbon molecules back to the abiotic
environment, for all living things are composed of organic molecules that contain atoms
of carbon element.
 The role of producers: 6CO2 + 6H2O C6H12O6 + 6O2
 The role of consumers:
Herbivores eat plants or algae to break down complex organic molecules, which
can be reassembled into the specific organic molecules that are part of its
chemical structure.
The carbon atom, which was once part of organic molecule in a producer, is now
part of an organic molecule in an herbivores.
During the process of respiration, the oxygen in atmosphere is used to break
down large organic molecules into CO2 and H2O.
Energy stored in chemical bonds is released by respiration and is lost as heat.
By the same token, the same processes occur when carnivore eats herbivore.
 The role of decomposers: Decay process of decomposers involves respiration and
releases CO2 and H2O back to the nature through recycling.
 The role of fossil fuels: Coal, oil, and natural gas are part of the carbon cycle.
Organisms were buried and the organic compounds in their bodies were modified
by geologic forces.
The C atoms present in the fossil fuels were removed temporarily from the
active, short-term C cycle. When fossil fuel are burned, the C reenters the active
C cycle.
 Nitrogen Cycle: The cycling of N atoms between the abiotic and biotic components and
among the organisms in an ecosystem.
 Very Few organisms are able to use tightly bonded N2. It must be in the forms of
NO3- or NH3.
 The Role of Nitrogen-Fixing Bacteria:
1) Able to convert N2 that enters the soil into NH3.
2) Free-living nitrogen-fixing bacteria.
3) Symbiotic nitrogen-fixing bacteria: Having mutualistic relationship with
certain plants (peas, beans, clover, etc) and certain trees (alders, etc.)
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 The Role of Producers and Consumers:
1) Construct proteins, DNA, and other important nitrogen-containing compounds.
2) When herbivores eat plants, the plant protein molecules are broken down to
amino acid, a smaller building block.
3) Amino acids are reassembled to form proteins typical for the herbivores.
4) Same process is repeated throughout the food chain.
 The Role of Decomposers and Other Bacteria:
1) Involve in nitrogen cycle by breaking down nitrogen-containing organic
molecules, releasing NH3, which can be directly used by many plants.
2) Nitrifying bacteria converts NH3 to NO2-, which can be converted to NO3- to be
used by plants.
3) Denitrifying bacteria: Able to convert NO2- to N2 when O2 is absent. N2 is
ultimately released into the atmosphere.
 Unique Features of the Nitrogen Cycle: (Fig. 5.30)
Two significant differences from C cycle
1) Most of the difficult chemical conversions are made by bacteria and other
microorganisms.
2) There is a secondary loop in the cycle that recycles nitrogen compounds
directly from dead organisms and wastes directly back to producers.
 Agriculture and Nitrogen Cycle:
1) In naturally occurring soil, nitrogen is often a limiting factor for plant growth.
2) To increase yields, farmers provide extra sources of nitrogen in several ways.
3) Inorganic fertilizers are the primary method of increasing the nitrogen
available.
4) Alternate planting between soybeans (nitrogen-yield crops) and corns
(nitrogen-demanding crops).
5) Using composts from plants and manure from animals as fertilizers.
 Phosphorus Cycle (Fig. 5.31):
1) Phosphorus: A common element in plant structure.
2) Present in many important biological molecules: DNA, cell membrane, bones,
and teeth.
3) Different from C and N cycles in one important respect:
P is not present in the atmosphere as a gas.
The ultimate source is rock, from which P is released by erosion and
dissolves in water.
Plants use dissolved P to construct the molecules they need.
Animals obtain P by eating plants or other animals.
Decomposers recycle P back into the soil by decomposing dead organisms
or their wastes.
Soluble phosphorus compounds are ultimately precipitated as deposits and
geologic processes elevate these deposits and expose them to erosion,
making deposits available to organisms.
Waste products of animals often have significant amounts of phosphorus.
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Human Impact on Nutrient Cycles
 Burning of Fossil Fuel:
1) Releasing large amounts of CO2, causing change of climate.
2) Seeking to reduce energy use and deforestation.
3) Altering the nitrogen cycle by doubling the amount of nitrogen available today when
compared to pre-industrial times as heating O2 and N2 to high temperature to form
more N-containing compounds.
 Conversion of Natural Ecosystem to Agriculture:
1) Forest, wetland, and grassland ecosystems tend to store carbon for long periods,
while agricultural ecosystems store carbon only temporarily.
2) Converting to agricultural ecosystem has increased the amount of CO2 in the
atmosphere (linking to global warming) has disrupted the natural C cycle.
3) Use of fertilizers, labeling in order of N, P, and K, to increase crops production has
significantly altered several nutrients cycles.
4) C, N, P, K and other elements are cycled within ecosystems, as when crops are
harvested, these elements are removed.
5) Farmers not only return N, P, and K, they also analyze for other less prominent
elements and add them to their fertilizer mixture.
 Agricultural Runoff:
1) The nutrients in fertilizers are intended to become incorporated into the bodies of the
plants and animals that we raise for food.
2) Applying too much N or P as fertilizer or if applying at the wrong time, much of this
fertilizer is carried into aquatic ecosystems.
3) Raising large number of animals for food in concentrated settings results in huge
amounts of animal wastes that contain N and P to enter local water sources.
4) The presence of large amount of N and P in fresher water or salt water results in
increased rates of growth of bacteria, algae, and aquatic plants, which lead to low
oxygen concentration and many organisms die. When decomposers use oxygen from
the water as they break down the dead organic matter.
5) Many algae are toxic and when their numbers increase significantly, fish are killed
and incidents of human poisoning occur.
6) Fertilizers use in the agricultural center of USA results in death of fish in the Gulf of
Mexico. (Fig. 5.32)
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