Interactions of living Things
SECTION 1
When we look closely at our surrounding environment, we find that everything (all
organisms and object) is connected in one or more ways. If one of the connections is
broken, the impact is often detected by observing many different organisms and what
happens to organisms when a “connection” is manipulated. Most of the time we look at
organisms in our environment and only “see” only organisms that eat other organisms.
We seldom pay much attention to some of the other factors we will learn about during
our study of the environment.
The living organisms in the environment are dependent on other living organisms for
food sources and survival. We are going to learn that these interactions form what is
known as a food web(s). Scientist that study these interactions within the environment
and we call these scientists ecologists. We must ask ourselves “what is ecology?” and we
will find out that ecology is the study of the interactions between organisms and their
environment.
The Environment
The environment is made of two things, nonliving things and living things. We have
special terms for these. Nonliving things are referred to as abiotic; these include rocks,
weather factors, the type of soil, the amount of light, and the temperature. The living part
is referred to as biotic. Biotic factors include all the living organisms that live together
and interact with each other.
Practice: Consider a pond, list as many biotic and abiotic factors that someone may find
at a pond. Did you say: biotic may include the fish in the pond, birds around the pond,
maybe a beaver or muskrat, the small organism’s fish feed on, aquatic (water) plants,
maybe algae? What about abiotic: you may have listed the mud on the bottom of the
pond, the rocks in and around the pond, the water, the temperature of the water, the
amount of sunlight the pond gets, the shade if there are trees bordering the pond? You
may have other biotic and abiotic factors listed, but the main idea is to learn what the
terms biotic and abiotic means and give examples of the terms.
The Organization of an Environment
RECALL: remember the organizational levels of organisms? Cells make up tissues,
tissues make up organs, organs make up organ systems and organ systems make up
organisms.
The environment also has levels of organization we can discuss. The first level contains
individual organisms. The second level is similar organisms that form populations. The
third level is different populations forming a community. The fourth level is the
community and its abiotic factors forming an ecosystem. And finally, all of the different
ecosystems make up the biosphere. Bio means life.
We must understand the definition of each level in order to understand how they are all
connected.
Populations – A population is a group of individuals of the same species that live together
in the same area at the same time. Example: All of the white-tailed deer in Catoosa
County. These deer compete with each other for resources (food, water, space, etc).
Communities - A community consists of all of the populations of different species that
live and interact in an area. The different populations will be depending on each other for
food, shelter and other things. All of the various animals and plants in an area make up
the community in a given area.
Ecosystems – An ecosystem is made up of all the communities found there as well as the
abiotic factors in the area. Ecologists that study ecosystems must look at the interaction
between living organisms and the nonliving objects in order to get a good understanding
of how the ecosystem functions.
Biosphere – The biosphere is the portion of the Earth where we find life. The biosphere
extends to the deepest parts of the ocean to very high in the atmosphere, where tiny
insects and plant spores drift. The biosphere includes all ecosystems.
Section 2 – Living Things Need Energy
In order for living things to survive, they must all have energy available to them.
Organisms use energy to carry out daily activities, heal themselves if they become hurt,
and reproduce offspring. Organisms can be grouped into three categories based on how
they obtain their food. These three categories are producers, consumers and decomposers.
Producers – These organisms are capable of producing their own food, most often by
carrying out photosynthesis (plants and algae). In the last 15 years scientists discovered
that there are organisms producing their own food from deep ocean vents where the
element sulfur is released from the Earth. There are bacteria that capture the sulfur and
make their own food from it and the bacteria serve as food for other organisms that
survive at these great depths. On land, (terrestrial environment) plants carry out
photosynthesis and are the main producers. In our oceans, algae that carry out
photosynthesis are the main producers.
Consumers – Consumers are organisms that cannot produce their own food. Consumers
must eat other organisms in order to get food. We will look at several types of consumers.
These include herbivores, carnivores, omnivores and scavengers.
Herbivores – these consumers eat plants for their food source. Examples: cows, bison or
buffalo, grasshoppers, muskrats, and some rodents (groundhogs). Carnivores – these
consumers feed upon other animals, so they eat meat. Omnivores – these consumers feed
upon both plant and animals as their food source. Scavengers – scavengers are animals
that feed on bodies of dead animals. Example: Turkey vultures (some people call them
buzzards) feed on dead animals. In aquatic ecosystems, crayfish (crawdads), snails,
worms and crabs can be considered scavengers.
Decomposers
Decomposers are the organisms that obtain their energy by breaking down the remains of
dead organisms. Bacteria and many fungi can be considered decomposers. Decomposers
are very important to an ecosystem because they return the dead organism’s nutrients
back into the ecosystem so other organisms can benefit from the nutrients. You could
think of decomposers as natures “recyclers”.
Food Chains and Food Webs
A food chain is a “flow chart” that shows how energy flows from one organism to
another and through the ecosystem. A food chain shows what organism another organism
consumes. Example: Imagine there is some clover growing on the ground and a mouse is
eating the clover. A snake slithers from the nearby tall grass and catches the mouse and
eats the mouse, but before the snake gets back into the tall grass to hide a hawk swoops
from the sky and captures the snake and eats the snake. The food chain would be
represented by: clover > mouse > snake > hawk.
Most food chains can overlap because many organisms feed on several different foods.
When food chains overlap, we say there is a food web. A food web shows us many
pathways that energy can flow through an ecosystem. The energy always flows in a oneway direction in the ecosystem. Energy an organism does not immediately use is stored
in the organism’s tissue(s). Only the energy that is stored in an organism’s tissue(s) can
be used by the next consumer. This leads us to the question of “how much energy can be
passed from one consumer to the next consumer?” We must look at food pyramids to
understand this concept. Some people refer to these as energy pyramids.
Energy Pyramids
Imagine the shape of a pyramid. The base is very wide compared to the pointed tip. Now
imagine the lowest area near the base is where producers are located. The next level up
the pyramid you will find a consumer that feeds on the producer represented at the
pyramids base. This consumer is called the primary consumer (meaning the first
consumer of the food chain the pyramid is representing). The next level would be the
secondary consumer meaning the second consumer on the chain, the following level is
the tertiary (meaning third) consumer. With our previous example, the clover is the
producer and the base level of the pyramid. The mouse is the primary consumer, the
snake is the secondary consumer, and the hawk is the tertiary consumer. Most energy
pyramids only have four or five levels. REMEMBER: only the energy stored in the
tissues of an organism can be transferred to the next level.
As you proceed from one level to the next higher level, the energy that can be transferred
becomes less and less. As a rule, only about 10% of the energy can be transferred from
one energy level (pyramid level) to the next higher level.
Example: if the clover provided the mouse with 1,000 calories, the snake could only gain
about 10% of these when it consumed the mouse (100 calories), when the hawk
consumed the snake, it could gain about 10 calories. In other words only 10% of the
energy is available from one consumer to the next higher consumer.
The energy pyramid also gives us some other information. The wide base represents a
larger number of organisms than the next level. So there must be more clover plants than
mice and more mice than snakes and more snakes than hawks as we go up the pyramid. If
it were the opposite, there would not be enough organisms to support the next level with
sufficient calories (food) so the food chain would collapse.
Habitat and Niche
These are two terms that are important to an ecologist because it gives an indication of
the food types available for an organism and what the function of the organism is in the
environment. An organism’s habitat is the environment in which the organism lives
(forest, desert, swamp, marsh, etc.) An organism’s “role” or way of life is the organism’s
niche. An organism’s niche includes its habitat, its food, its predators, the organisms it
competes with for survival. The niche can also include the abiotic factors like
temperature, light, and moisture.
We will read about the Grey Wolf and find out that it is a consumer. It is a carnivore and
will eat animals from the size of a moose down to a rat when given the opportunity. We
will also learn that Grey Wolf has a social structure within the group the wolf lives, and
other groups of wolves are enemies. Two of the wolves in the pack will be the lead
wolves and the others will follow their “lead”. We will also learn that Grey wolves care
for their young and teach them how to hunt and survive. The Grey Wolf is also an
important part of the ecosystem that they live in. They often keep the larger herbivore
population (moose, elk and deer), as well as other population “in check”.
SECTION 3
Types of Interactions
Within nature the interactions between populations of different species affect the
population sizes. (Some organisms regulate the population of others by feeding “preying”
on other organisms). Example: in the arctic tundra, there are small rodents (similar to
hamsters) called lemmings. The lemmings are eaten (preyed upon) by arctic foxes and
other animals. The animals that prey on lemmings help control the lemming population
size.
Having Offspring
In nature, most organisms have more offspring than can survive. Example: A fish may
lay hundreds of thousands of eggs, but all of the eggs will not hatch. Some of the eggs
may be preyed upon before they hatch. In most situations, the population of organisms
remains fairly constant in nature unless rare conditions occur that supplies more food for
a larger population than normal. We will discuss one such population in class.
Limiting Factors
Populations of organisms cannot continue to get larger and larger (grow) due to limited
food, space, water, and other resources the organism needs. These resources (biotic and
abiotic) serve as limiting factors. (Limiting factor – a resource that is needed, but is in
limited supply). Any needed resource can become a limiting factor if the organism cannot
get enough of the resource to survive.
Carrying Capacity
The largest population that an environment can support over a long period of time is
known as carrying capacity. When populations grow larger than the carrying capacity,
limiting factors occur and some of the population will die due to limited resources.
If the limiting factors continue to decline, the population must decline also. As soon as
the environment “improves” and the limiting factors return to “normal”, the population
size will also increase and return to “normal.
Interactions Among Organisms
Populations have interactions between their own species and other species in the
environment. Example: Grey squirrels interact when they feed in the same area, so this is
an example of the same species interacting together. Grey squirrels may also interact with
different species. Example: an Great Horned Owl may see a Grey Squirrel as food and
capture and eat the squirrel. Many interactions such as this occurs everyday in the
environment(s) that are on Earth. These interactions are necessary for life to continue.
Interactions may take the form of competition for food, space, mating partners, water,
and living space for example. Interactions may also take the form of predator prey
relationships (one organism capturing and eating another organism).
Competition
Again populations in a community can have competition among the same species, or you
can also find competition between different species. An example of competition between
different species could be Grey squirrels and White-tailed deer competing for the
available acorns for the main food source at times of the year. Remember competition
can be in the form of organisms competing for the same space, food, shelter, and even
sunlight (especially plants). So we must remember that competition can be within the
same species as well as between different species.
Predators and Prey
An organism that is eaten by another organism is called prey. The organism that is eating
is called the predator. When a fish eats a worm, the fish is the predator and the worm is
the prey.
Predator Adaptations
In order for predators to survive, they must be able to capture prey. Some predators run
fast in order to accomplish this, others may be excellent at hiding, others may be
excellent stalkers to capture prey. Different predators have different methods and
adaptations to capture their prey.
Prey Adaptations
Prey organisms have also adapted to keep from being eaten. Methods prey have to avoid
capture is to run fast, stay in groups, and some have adapted camouflage methods. Some
prey are poisonous to predators and so they are not eaten. Some preys have bright colors
that warn prey that they should stay away. Examples: fish often stay in small schools
which give the illusion that they are one large organism and this can scare predators
away. Antelopes and buffalo remain in herds for protection. When you have many
organisms, they all serve as lookouts because each organism will be using sight, hearing,
and smell to avoid being eaten. Some prey hide by using camouflage, some look like
leaves, some may resemble sticks, and some may look like tree bark. We may discover
other examples of camouflage as we study the environment.
Symbiosis
Symbiosis is a close, long term association between two or more species. The individuals
in a symbiotic can benefit from, be unaffected by, or be harmed by the relationship. Often
one species lives on or in another species when a symbiotic relationship occurs. There are
three specific types of symbiotic relationships in nature. These are 1) mutualism, 2)
commensalisms, and 3) parasitism.
Mutualism
A symbiotic relationship in which both organisms benefit is called mutualism. Example:
we have a species of bacteria that live in our intestines that produce certain vitamins for
us and the bacteria get nutrients form the food we eat. Humans and the bacteria benefit
from the relationship.
Commensalism
Commensalism occurs when there is an symbiotic relationship in which one organism
benefits and the other is unaffected by the relationship. An example is a fish that rides
under a shark waiting on the shark to eat something and get the “tidbits” the shark loses.
These fish are called remora fish. The shark is not harmed in the relationship.
Parasitism
In this symbiotic relationship, one organism benefits and the other organism is harmed.
The organism that benefits is called the parasite and the organism that is harmed is called
the host. The parasite gets nourishment from its host and the host will become weak over
time and often so weak the host dies. Examples of parasites are ticks, tapeworms, leeches,
and many organisms called roundworms. Can you think of any parasites and hosts that
share this form of relationship?
Most parasites do not kill their host or they would have to find another host to survive
within. If the parasite killed the host organism it may not be able to find another host to
live in or on and the parasite itself may die.
Coevolution
Coevolution is a long term change that takes place in two species because of their close
interactions with one another. Coevolution sometimes occurs with herbivores and the
plants they feed on. The acacia tree and a species of ant have evolved together. The tree
produces a form of food for the ant and provides a place for the ants to live and the ants
protect the tree by attacking herbivores that try to feed on the tree.
Coevolution and Flowers
Some of the most amazing examples of coevolution are between their pollinators. A
pollinator is an organism that carries pollen from flower to flower. Examples of
pollinators: hummingbirds, butterflies, and bees. These organisms gather nectar from
flowers and in the process they get pollen on themselves and when they visit the next
flower, they leave some pollen on the flower and this helps fertilize the flower to produce
fruit. The pollinators are attracted to the flowers by color, scent, and the nectar. When the
pollinator places its head into the flower for the nectar, some of the pollen there attaches
to the pollinator and is transferred to the next flower the pollinator visits.
SECTION 1 STUDY GUIDE
1. The scientists whom study the interactions (connections) of
the environment are called e_______________________.
2. The study of the interactions between organisms and their
environment is called e___________________________.
3. The living organisms that interact with each other in the
environment are considered the b_____________________
part of the environment.
4. The nonliving things in the environment (water, air, soil,
rocks, etc.) are considered the a________________ part or
factors.
5. List the levels of organization in the environment. You
should list five levels. 1) Individuals of the same species
make up 2) p
, populations make up 3) c
, ________________ communities make up 4) e________
, ecosystems make up 5) b
.
6. A group of individuals of the same species that live together
in the same area at the same time is recognized as a
p_________________________.
7. C____________________ consists of all of the populations
of different species that live and interact in an area.
8. An e____________________ is made up of a community of
organisms and its abiotic environment.
9. The part of the Earth where all the life forms are found can
be called the b_______________________. (It may extend to
the bottom of the ocean to high in the atmosphere).
10.
Give two examples of biotic and abiotic objects.
SECTION 2
1.
All living organisms need e________________ in order to
survive. They need the energy for reproducing, moving,
growing and taking care of their offspring.
2.
List the three groups of organisms based on how they
obtain their food (energy). C
, and D
3.
,P
.
Organisms that use sunlight to make (produce) their own
food are called p____________________.
4.
List three examples of producers.
5.
What are the main producers of the ocean?
6.
What are the main producers in terrestrial (land based)
ecosystems?
7.
All organisms that eat producers or other organisms can be
called c__________________________.
8.
A consumer that feeds on producers (plants) are called
h_________________________________.
9.
Organisms that eat other animals are called
c_____________________.
10. O_______________ are organisms that feed on plants and
animals.
11. D_________________ are organisms that feed on the
bodies of dead animals.
12. Organisms that get energy by breaking down the remains of
dead organisms are called d____________________. We
can say these organisms are the recyclers of nutrients in
the environment.
13. A e______________ p___________________ represents
how the energy in food molecules from one organism to
the next also can be a food chain.
14. When there are many pathways represented in which
energy flows from one organism to the next, we refer to
this as a f______________ w__________.
15. Energy always flows in a o________________
w_________________ direction through the environment.
16. Only the energy stored in an organism’s
t________________ can be passed to the next consumer.
17. As you look at an energy pyramid and go toward the top,
the amount of available energy
i_________________________. (increases or decreases).
18. Only the energy stored in an organisms
t________________ can be passed from one organism to
the next consumer.
19. An organism’s h______________________ is the
environment in which the organism lives.
20. An organism’s role or way of life is the organism’s
n_________________.
21. What type of consumer are Grey wolves (omnivore,
herbivore, or carnivore)
22. KNOW: Grey wolves have a social structure and there are
usually two leaders that the other wolves “follow”. Each
member of the pack has a particular rank and position.
Some of the wolves hunt for food and some baby sit the
young. At about 2 years of age the young wolves leave the
pack and try to find their own mates and start new wolf
packs. Wolves and other predators are very important to
maintaining the proper number of prey organisms.
Predators often control prey population sizes so they are
very important in the food web.
SECTION 3
1. Most organisms produce (more or less) offspring than can survive.
2. A resource that can influence a populations size can be called
l_________________ f_________________. (limits the population size).
3. List four ways that organisms affect each other?
4. When two or more individuals or populations try to use the same limited
resource, such as food, water, shelter, space, or sunlight is called
c____________________.
5. Explain how competition can occur between organisms of the same species as
well as organisms of different species.
6. An organism that is eaten by another organism is called p_________________.
7. An organism that has captured and is eating another organism is called a
p____________________________.
8. Describe or list some methods that predators have adapted in order to capture
prey.
9. What are some methods that prey organisms avoid becoming a predators dinner?
10. A close, long term association between two or more species is called
s____________________.
11. List and explain the three groups of symbiotic relationships.
12. Explain and give an example of coevolution.