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Ecology
The Ecosystem
Ecology – the study of organisms in their habitats
People who study ecology – ecologists
Ecology divided into three relationships: How organisms affect each other How nonliving factors of an environment (such as
light, temperature, water, soil, and wind) affect an organism
How organisms affect the nonliving factors of a habitat
The Ecosystem
Ecosystem – a limited area in which living and nonliving things interact Example: a meadow
Ecosystems are made up of two major parts: Abiotic environment
Physical environment Nonliving factors in an ecosystem
Biotic community All living organisms in an ecosystem
The Ecosystem
Habitat – the area where an organism lives, which supplies the organism’s needs, which include food, water, oxygen, shelter, and more
Every living thing has a role in their ecosystem
Niche – what an organism does (its “job”)
Artificial ecosystem – an aquarium (man-made)
The Abiotic Environment
Five major abiotic factors Light Temperature Water Soil and Substrate
Soil contains varying amounts of sand, silt, and clay
Wind or current
The Abiotic Environment
The Water Cycle (p. 362) The continuous movement of water from the
atmosphere to the earth and back to the atmosphere Two main stages of the ecosystem – evaporation and
precipitation Evaporation – movement of water from the earth to
the atmosphere Precipitation – as water evaporates, it enter the air as
water vapor – when it falls back to earth Runoff – when precipitation reaches the ground and it
seeps in the soil or moves along the surface of the earth
Groundwater – when precipitation enters the soil Water table – when groundwater collects in the earth,
forming a reservoir Cyclic – meaning occurs in cycles
Succession
Succession A series of changes that occur in biotic communities as
they progress toward a climax community Pioneer species – organisms that live in an area in the
early stages of succession Climax community – the stable population of plants
and animals found in an area if it is left undisturbed for a long period of time
What causes succession? Natural disasters Humans (building)
The Biotic Community
Made up of all the living things in an ecosystem
Natural ecosystems are much more complex than artificial ones
Levels of organization Individual organism – the most basic level of
organization Population – all individuals from the same species in
an ecosystem Community – all the populations in a given area Ecosystem – biotic community plus the abiotic
environment it inhabits
The Biotic Community
Population types Populations in a biotic community can be divided into
two main types: Producer organisms (autotrophs)
Manufacture their own food Carry on photosynthesis Ex. plants
Consumer organisms (heterotrophs) Cannot manufacture own food Obtain energy from other sources Ex. rabbit, owl, etc
The Biotic Community
Limiting Factors Control the size of certain organisms in certain areas Ex. rabbit and lynx A factor in a habitat that limits the growth or
existence of a species
The Carbon and Oxygen Cycles These cycles use two major biological processes:
photosynthesis and cellular respiration Oxygen and Carbon dioxide are two gases passed
back and forth between photosynthesis and cellular respiration
Photosynthesis – plants only – take in carbon dioxide and give off oxygen
Cellular Respiration – ALL organisms
The Biotic Community
The Nitrogen Cycle All living things need nitrogen to survive and
reproduce 78% of the atmosphere is nitrogen Nitrogen cycle is a process designed to convert
nitrogen into a usable compound Nitrogen from the atmosphere is brought to earth
thru rain and absorbed in the soil where bacteria turn it into a usable form
It helps plants grow and when animals eat the plants, they take nitrogen in to use it in their own bodies
Rhythms in the Ecosystem
Populations are active at different times throughout the day and season
Rhythms – changes that happen on a regular basis in an ecosystem Daily rhythms – 24 hrs Seasonal rhythms – repeat every year
God established these on day 4 of creation
Circadian rhythms Circadian (daily) is a change that takes place every
24 hr period Nocturnal – enter into a period of rest Diurnal – enter a period of activity
Temperature and other factors affect these Ex. Why some flowers bloom at night and not
during the day (morning glories)
Rhythms in the Ecosystem
Biological clocks “internal clock” that works with or without daily light
changes Mostly animals, but plants do as well
Seasonal Rhythms A change in the ecosystem that occurs with the
change of season (usually once per year) Temperature change and amount of water available
are two of many factors that change seasonally Dormant – when plants or other organisms stop
growing or become inactive for a period of time
Seasonal Changes in Animal Populations Migration, hibernation (state of deep sleep), dormant
stages in their life cycle
Energy Exchange Between Organisms
Organisms have many different relationships
An ecologist needs to understand these relationships in order to decide what is happening in an ecosystem
Matter is cyclic in an ecosystem, but NOT energy
Living things lose much of the energy they use
Once energy is lost, living things cannot used it again to live
Since energy is not cyclic, an ecosystem must constantly supply its organisms with useable energy
For most ecosystems, this supply of energy comes from plants and algae that receive sunlight.
22A.1 Food Chains, Food Webs
The passing of materials and energy from one organism to another is called a FOOD CHAIN
Every living thing is at least a part of one food chain
Producer organism – First organism in the food chain; makes its own food and food for others (autotrophs)
Consumer organism – the rest of the food chain organisms; Heterotrophs, rely on other sources for food.
Food chains end with a consumer called a DECOMPOSER ORGANISM – usually bacteria or fungi that break down the remains of dead organisms and return that material to the soil
22A.1 Food Chains, Food Webs
Food Web – Interrelated food chains that are connected in different ways in an ecosystem (see p. 377)
Studying a food web gives a more accurate picture of what happens in an ecosystem than a food chain does
22A.2 Ecological Pyramids
Ecologists often use ecological pyramids to illustrate energy relationships in a food chain
It is divided into layers that represent a different type of organism in the food chain.
Bottom layer – largest – represents producer organisms because all other layers depend on the producer organisms for energy supply!
Second level – herbivores – organisms that eat plants (less energy available at this level)
Third level – Carnivores – animals that eat other animals (even less energy available)
22A.2 Ecological Pyramids
The loss of energy that takes place in an ecological pyramid can also be explained in the fact that in each level of the ecological pyramid, organisms use about 90% of the energy they receive, which leaves only about 10% of the energy for the level above!
To supply enough energy for all levels, the producer level must be very large!!
Biomass – dried mass of the living matter in a given area of the habitat
22A.3 Problems with Ecological Pyramids
They are models that help show the energy relationships between populations in an ecosystem
BUT, relationships other than a straight food chain make constructing an ecological pyramid difficult.
First factor – the presence of Omnivores Omnivores – organisms that eat both plant and
animals ex. Raccoons, bears, opossums, humans
Second factor –eating habits of some carnivores Some eat herbivores and other carnivores! Example – hawk eats rabbit (herbivore) and then
a snake (carnivore) Because it eats both, it may be found in two
different levels of the ecological pyramid!
22A.3 Problems with Ecological Pyramids
Third Factor – movement of many organisms from one ecosystem to another
As they move, they become a part of different food chains!
These three factors are only some of the problems ecologists must deal with while studying the flow of energy in ecosystems
22A.4 Predator-Prey Relationships
Predator – an animal that feeds on other animals
Prey – the animal the predator eats!
Predator-prey relationships help keep the populations balanced within an ecosystem
Complete Section Review 22A and Ideas 22A-B
22B Relationships between organisms of the Same Species
The passing of energy and nutrients from one organism to another is one of the primary relationships between organisms
To study the other relationships, ecologists divide them into two groups: Relationships between organisms of the same
species Relationships between organisms of different
species
22B.1 Independent Organisms
Independent Organism – one that exists without the aid of other members of the same species Examples: Spiders, bears
22B.2 Couple Relationships
Some animals choose a mating partner and rarely separate from that partner.
Called “mating for life”
Some birds mate for life Examples: Bald eagles, penguins, owls,
parrots, sea birds, swans
Some fish - angelfish
22B.3 Animal Societies
Animal society – forms when a number of animals fro the same species live together
It provides a means of defense Example: A school of fish, flock of birds, herds
of oxen or elephants, pride of lions Other terms: gaggle, pod, gang, sounder,
mob
22B.4 Social Insects
Animals of the same species often form groups
Some of these groups have well-defined roles for their members.
Social insects: Ants – 1 queen per colony; worker ants that
work to repair, build, ad defend the nest; others care for eggs; others search and gather food
Termites Wasps Bees
22B.5 Competition within populations
Competition – the struggle between organisms for some essential factor that is in short supply in the environment
Many animals compete for mates
Pecking order – a system of rank that occurs among a group of organisms
Compete for dominance in the group
Competition also refers to relationship between certain plants – but does not mean a struggle for survival. Compete for sunlight, food source, etc
22C: Relationships between different species
Predator-Prey and Parasite-host are examples
Competition between populations: Occurs when two or more different populations
have the same requirements Example: compete for space (habitat) or food
source Sometimes the ecosystem supports the two to
live together and they limit each other to stay balanced.
22C.2 Commensalism
A relationship between two populations that benefits one and does not hurt the other
Example: leopard kills antelope and eats, but the jackals and buzzards come “clean up”
Scavengers – animals that eat dead or decaying matter
Relationship between a scavenger and a predator is a great example of commensalism
Epiphytes – plants that grow on branches of trees, but do not take nourishment from the tree
22C.3 Mutualism
A relationship between two populations that is beneficial to both Example: bee gathers nectar and pollen from
flower and flower is pollinated by bee
Obligatory mutualism – both organisms must be together or they will die Example: Lichens
Natural Resources
23A Living things as Natural Resources
God has placed man on a planet with abundant natural resources
Natural resources: useable materials that man can obtain from the physical world. Includes: plants, animals, land, water,
substances from the ground (such as coal, oil, gems, and metals) and even features of the ground (hills, prairies, and coastlines)
Some natural resources are RENEWABLE (can be replaced – ex. trees) and other NON-RENEWABLE (cannot be replaced; once its gone, its gone; ex. oil, coal)
23A Living things as Natural Resources
The living things that share our planet are a type of natural resource
Plants are more than decorations and animals are more than pets
Humans rely on three types of organisms: Producers – trap energy from sun and convert
it into food critical to the survival of animals and humans; plants are also used to produce fiber for clothing, materials for building, and even medicines
consumers decomposers
23A Living things as Natural Resources
Humans rely on three types of organisms: Consumers – provide food, transportation, and
labor as well as fibers and skins for clothing and other products
Decomposers – are important in removing and recycling wastes. Without bacteria, fungi, and worms, all ecosystems would stop functioning
As the human population grows, man’s abuse of these natural resources can have long-lasting effects.
23A.1 Man’s use of wildlife
The fur-trading industry is an example of man’s unwise use of wildlife
Beavers were among the most sought-after fur-bearing animals in early decades – but trapping became unprofitable. Had it continued, American beavers might have become extinct
Extinct – when there are no members of a species left alive on earth
In the past, hunting was a main source of supply for food; today, it is primarily a sport. Wildlife management agencies are in place for the purpose of protecting species and controlling populations of species
23A.2 Farming
Farming – caring for a concentrated group of plants and animals so that they can be used to supply human needs
Farming gives man the product he needs without reducing the natural population of organisms
Ex. corn, wheat, pigs, chickens, etc
Domesticated organisms – those living things that man primarily raises for his own use
23A.3 Agriculture and the Soil
Agriculture – the science of growing crops and livestock
Agricultural scientists have studied what different crops require to produce large harvests; thus they experiment with the genetic make-up of various crops
Often when people first moved to an area, they prepared the land for farming back in the day
But overuse of the soil can cause it to be unproductive and lose its fertility!
23A.3 Agriculture and the Soil
A way land can lose its productivity: Depletion of soil nutrients
How farmers overcome this issue today: Fertilizer – a substance that contains the
nutrients needed by plants (add this to soil Crop rotation – a method of farming in which a
farmer changes the kinds of crops he grows in a particular field every year or two; helps to prevent nutrient depletion
No-till agriculture – cultivate the soil as little as possible and harvest only the seeds or fruits
23B Man’s Role in the Ecosystem
Exponential growth – describes a constant rate of dramatic increase
Human population – number of people living on the earth at one time – has experienced exponential growth
How a population grows Birth rate – rate at which members enter a
population Death rate – rate at which members leave a
population Both affect population growth
If birth rate and death rate are the same = 0 population growth
If death rate increases or birthrate decreases – population growth decreases
If birthrate increases or death rate decreases – population increase
23B.2 Doomsday Ecology
Some ecologists predict a horrible doomsday when humans will ultimately destroy the earth by their abuse of the physical world
These people believe the earth will become so overpopulated that there will be an overwhelming demand for natural resources; as supplies decrease, people will struggle to meet their needs
According to these people, people will pollute almost all the earth with wastes and poisons
Global warming is another issue – drastic predictions about ice caps melting, sea levels rising, and major coastal cities being flooded
Most connect this issue with the increased use of fossil fuels and carbon dioxide added to the atmosphere
23B.3 Planning for the Future
It is difficult to predict how large the human population will be
In the past, natural disasters, wars, and epidemics have all had a drastic effect on population growth
Even if population does continue to grow, the earth still may be able to provide enough food for the human race (technology, productive crops, etc)
It is estimated that today, farms can produce enough food to feed up to 100 billion people, yet people are dying of starvation!!
Political problems, poor farming techniques, and wasteful food practices are just some of the factors that contribute to the problem
Death by starvation is slow, humiliating, and painful
As Christians, we are called to love our neighbors – what can YOU do to be a part of solving this problem of hunger?
23B.4 Conservation
Conservation is the preservation and wise use of natural resources
Ecologists and others who decide how to use natural resources must be informed about ecological matters to make wise decisions
National Parks and forests are a way of preserving land for protection and controlled use
Energy is a natural resource that must be conserved! Coal, oil, and natural gas are fossil fuels
Fossil fuels – remains of plants and animals that once lived on earth (these are NOT renewable)
23C Pollution
Pollution is the addition of impurities to an ecosystem
There are two major types of pollutants: Substance pollutants – a solid, liquid, or gas that
pollutes an ecosystem 2 types:
Biodegradeable- those substances that living organisms can break down Sewage, paper, wood products
Nonbiodegradeable – substances the environment cannot break down Plastic, glass
Energy – any form of energy that pollutes an ecosystem Heat, light, sound, and radiation
23 C Pollution
Water Pollution Can have drastic effect on humans Water means of spreading intestinal infections
and diseases (cholera, dysentary, hepatitis) Many water pollution problems result from
sewage
Air Pollution Carbon Monoxide – most abundant component of
air pollution Sulfur compounds Nitric Oxide Smog – combo of smoke, auto exhaust, and fog
Trash – solid materials that are either useless or unwanted Landfills, recycling
