The Interdependence of Ecosystems Name - Bucyrus City ...

The Interdependence of Ecosystems Name _______________________________

Relationships in an Ecosystem

Many relationships exist in our ecosystems.

Think about the meanings of the words dependent and independent as they relate to variables. What do

you think interdependence means in terms of organisms that live together in an ecosystem?

Invasive species are organisms that aren’t native to an ecosystem. Humans introduce invasive species

into an area on purpose or by accident. At times, organisms move into an area because of loss of habitat

or other environmental changes. Do you think invasive species affect the native species in an

ecosystem? Why or why not?

Biotic and abiotic factors make up an ecosystem. Green plants, or produce rs, make their own food. They

act as the source of energy for the ecosystem. Some organisms obtain energy from these producers.

These organisms are the primary consumers. They give energy to the next level of consumers, creating a

food web. When an organism dies, microbes such as fungi and bacteria act as decomposing agents. They

decompose dead organisms and return valuable nutrients back to the ecosystem to start the entire

process again.

So, the living beings in an ecosystem depend on each other for their survival and growth. This

dependency is known as interdependence. All living beings, from tiny microbes to huge predators,

depend on each other to obtain energy and other basic resources. Living beings also depend on abiotic

factors such as sunlight, water, and air for their existence.

Plants produce energy, and consumers eat plants. Later, fungi act as decomposers and break down dead

organisms.

Predator and Prey Relationships

In an ecosystem, the relationship between a predator and its prey is of utmost importance. The number

of predators in an ecosystem balances the population of prey. In the activity, we saw that as the lionfish

population increased, the populations of lower consumers decreased. A decline in the number of

predators for a particular prey will cause the population of prey to grow out of control. The increase in

prey population may lead to a lack of food, resources, and shelter for the organisms.

Consider an ecosystem where frogs eat insects and snakes eat frogs. An increase in human activ ities

leads to the death of snakes. The population of frogs then increases beyond control because there are

fewer snakes to eat them. This increase leads to a decrease in the number of insects and disturbs the

balance of the ecosystem.

The lynx is a predatory cat that depends on the snowshoe hare for food. Review the trend in the graph.

What happens when the population of one species changes? What does this trend say about the

interdependence of these two species?

Types of Relationships

All living beings coexist with each other. However, some species share close relationships with other

species. Scientists define these close relationships as symbiosis. Three main types of symbiotic

associations exist in an ecosystem.

Mutualism

Mutualism is a beneficial symbiotic relationship between two species. Both species benefit from this

relationship. The most well-known example of mutualism is the association between flowering plants

and bees. Another example of mutualism is the relationship between certain fungi and trees. Some fungi

grow on the roots of trees. They penetrate into the roots and establish a symbiotic relationship called

mycorrhiza. The trees produce energy through photosynthesis and share the energy with the fungi. The

fungi act as decomposers and break down dead organic matter to provide nutrients for the trees to

grow.

Species involved in mutual relationships exhibit different levels of interdependence. In some cases, both

species can survive by themselves. However, they gain mutual benefit when they work with each other.

This relationship is called facultative mutualism. Sea anemones and clown fish have a facultative

mutualistic relationship, for example. Sea anemones provide protection to clown fish. The fish provide

the sea anemones with nutrients. Isolating either organism won’t completely wipe out the other

organism.

In obligate mutualism, two species are completely dependent on each other for their survival. If one of

the species dies, the other species will die too. An example of obligate mutualism is the relationship

between termites and their intestinal flagellates. The flagellates provide enzymes for the termites to

digest cellulose, which helps them survive. In turn, the termites provide nourishment to the flagellates.

However, if one of them is isolated, the other will die from lack of nutrition.

Commensalism

In a commensal relationship, a species obtains food or resources from another species, but the

association is neither beneficial nor harmful to the other organism. The species that benefits from the

host is the commensal. It is at a greater advantage because it can increase its chances of survival. The

host organism, however, has the same chance of survival. This relationship often exists between a small

commensal and a larger host.

One example of commensalism is the association between filter-feeding barnacles and whales.

Barnacles are small arthropods. Their larvae undergo stages of development and then settle onto hard

surfaces, such as a whale’s back. The whale provides these commensals with protection and access to

nutrients as it moves through the water. The whale, on the other hand, doesn’t benefit from this

relationship. The barnacles form a hard covering on the whale’s skin, but they don't hinder the whale’s

health or its ability to obtain food.

Parasitism

Parasitism is a harmful association between species. One of the two species obtains nutrients and

energy from the other, but the host organism is harmed in the process. Parasites aren’t always deadly,

but they do affect their hosts in a negative way.

Parasites can be endoparasites, which live inside the body of a host. For example, tapeworms are

parasites that live inside the host’s digestive tract. Tapeworms cause harm by feeding on nutrients in the

host’s stomach. Ectoparasites are parasites that live outside a host’s body. Ticks, fleas, mites, and lice

are all ectoparasites.

Science in the News: Bedbugs

“Sleep tight, don’t let the bedbugs bite” is a well-known saying that dates back at least a century.

Unfortunately, bedbugs are a problem once again.

Bedbugs are insects that feed on the blood of humans. Because of this behavior, they’re found on

furniture, clothing, and bedding. The spread of bedbugs has increased, and humans are partially

responsible. People travel internationally, which helps the bugs spread. If people who have bedbugs on

their clothing or luggage travel to new places, they can accidently transfer the bugs to new

surroundings. Bedbugs have adapted well to human surroundings. They can spread quickly and infest

places easily.

When bed bugs suddenly made a comeback in recent years, biologists were just as surprised as

everyone else. Few had studied the bugs because there seemed no need to do so. But as bed bugs

became ever harder to kill, scientists began probing hard to find their weaknesses.

To do that, they invited some of the bugs to stay in the lab. There, researchers could observe them

closely. But to be good hosts, the scientists had to keep their bugs healthy and well -fed. And that has

required learning how to deliver these critters the blood on which they thrive..

In the beginning, scientists didn’t know. But they figured a good first step was to recreate key features

of the human body. For instance, they worked to warm the blood to the right temperature . And they

had to enclose it in a skin-like membrane for the bugs to pierce with their needle-like mouths.

Scientists at the Ohio State University in Columbus took a short-cut. They turned to ready-made feeders

that had originally been designed to nourish other bloodthirsty insects in the lab: mosquitoes.

Still other scientists took a more old-school approach. They fed the bugs from their own arms and legs.

Harold Harlan became especially famous for this. A former entomologist with the U.S. Army, he had

found bed bugs at an army base in New Jersey. This was during the early 1970s. Back then it was very

rare to find any live bed bugs. So he brought some to his lab to study in his spare time. He raised them

on his own blood. And he still does so today — more than 40 years later!

Harlan has kept his bed bugs away from insecticides this entire time. As a result, these insects are more

sensitive to the chemical insect killers than are the bed bugs infesting our homes. And that makes his

critters quite valuable to scientists. Many ask to use some of his bed bugs in experiments to probe how

they differ from the poison-defying “super bed bugs.”

Harlan’s bugs also were the first to be used in two major projects aimed at mapping the bed -bug

genome. These studies are attempting to identify all of the different genes in this insect. Such

information could help scientists one day find ways to better control the pests.

The Bed Bug Genome Consortium is conducting one of the studies. Some two dozen researchers from all

over the world are collaborating on it. Scientists from Weill Cornell Medical College, the American

Museum of Natural History and Fordham University are taking part in a related investigation. (All three

of those institutions are in New York City.)

This research can be difficult. It also will likely take a long time to complete.

Power Words

bed bug A parasitic insect that feeds exclusively on blood. The common bed bug, Cimex lectularius,

sucks human blood and is mainly active at night. The insect’s bite can cause skin rashes and welts that

sometimes look like a mosquito bite, but different people react in different ways.

consortium A group or association of independent organizations.

entomology The scientific study of insects. One who does this is an entomologist

gene (adj. genetic)A segment of DNA that codes, or holds instructions, for producing a protein.

Offspring inherit genes from their parents. Genes influence how an organism looks and behaves

genome The complete set of genes or genetic material in a cell or an organism. The study of this

genetic inheritance housed within cells is known as genomics.

infest To create a parasitic community, such as when wasps infest the porch of an abandoned house.

Such a community of pests is known as an infestation.

Do you agree with the article’s assessment that bedbugs are parasites? Explain your reasoning using

what you’ve learned about parasitic relationships.

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Warm-Up

The availability of resources is one factor that greatly affects an ecosystem.

All living organisms in an ecosystem require resources for their growth and survival. List some resources

that you think plants and animals need.

Do you think the resources you mentioned are finite? Or are they in unlimited supply? Explain your

answer.

Competition for Resources

We all need resources from the environment for survival, regardless of where we live. The oxygen we

breathe is a resource. The plants and animals we consume to get necessary nutrients are resources. The

land on which we build houses is a resource too. Other organisms, from tiny microbes to large

mammals, also use resources from the environment for their survival.

Competition

Most resources in a habitat are limited in supply. So, organisms compete with one another to obtain

them.

Competition is intraspecific if two organisms of the same species compete for resources. And, if

organisms of two different species engage in a competition, it’s interspecific. Both types of competition

can be direct or indirect.

Direct Competition

When two birds fight over the same meal or two pets fight over the same bone or biscuit, they’re

engaging in direct competition. In this type of competition, an organism directly alters the resource

accessibility of the other organism. So, it’s also called “interference competition.”

Direct competition can occur within the same species. For example, a male bighorn uses physical

aggression to prohibit other males from accessing a mate. Direct competition can also occur between

members of different species. For example, two different animals can fight for the same meal. Direct

competition doesn’t need to be one-on-one. Several organisms can directly compete at once for the

same resource.

Indirect Competition

There are two types of indirect competition: exploitative and apparent.

Exploitative Competition

Sometimes, two organisms interact indirectly as they compete for the same resource. For example, two

predators that eat the same kind of prey may not interact directly with each other. However, they still

have an effect on each other’s food supply. Exploitative competition occurs when consumption of

resources by one species makes the resources unavailable for another species.

Exploitative competition can also be intraspecific. All the squirrels in an area are in indirect competition

with each other for nuts and seeds. They also compete for space to store their food for the winter.

If the population of either prey species increases, the increase has a positive outcome for hawks.

Apparent Competition

Apparent competition takes place when an increase or a decrease in the population of one of the prey

species affects the population of the predator. This impact subsequently affects the population of the

second prey species. For example, hawks eat mice and squirrels. If the population of mice increases, the

hawk’s population will also increase because of the abundant food supply. So, the larger hawk

population will negatively affect the squirrel population.

In an ecosystem, many organisms compete both directly and indirectly for resources. For example,

predatory birds may indirectly compete for the limited number of prey in an area. They may also

compete directly by trying to take food from another bird.

Organisms compete for limited resources at many levels. Match each scenario to the type of

competition it exhibits.

Factors That Affect Resources

A change in the number of resources in an ecosystem can affect the survival of one or more species that

live there.

Invasive Species

Invasive species are organisms—plants, animals, insects, and bacteria—that aren’t native to the

ecosystem in which they live. They compete with native organisms for food and other resources. Many

factors can cause an invasive species to enter a new ecosystem. Let’s look at a few of them.

Intentional Human Introduction

Humans have introduced some species into nonnative areas to help control pests that damage crops.

For example, the cane toad was introduced into many regions of the Pacific and Caribbean islands as an

agricultural pest control. Humans have transported many plant and animal species for other purposes

too. For example, the water hyacinth was introduced in Australia as an ornamental plant. Similarly,

some animal species are also brought to nonnative areas as pets.

Unintentional Human Introduction

Small mammals, insects, and other organisms can stow away in boats and trains. They can even lodge

themselves in shipping crates. For example, a Caspian Sea tanker accidentally introduced Asian zebra

mussels into the Great Lakes. Zebra mussels entered through the tanker’s ballast water and are now a

threat to about 140 native species. They’re also causing severe economic harm by damaging waterways,

harbors, and power plants.

Habitat Loss or Changes

Sometimes, certain species in an ecosystem face problems such as the loss of shelter, a reduced food

supply, and the unavailability of other resources. These changes can cause the species to travel to other

ecosystems for resources.

Invasive species have varied effects on native populations. Some invasive species affect native species in

minor ways, and others have a significant impact. Predators are natural “population controls” for many

species. If an invasive species has few natural predators, it can spread quickly. Invasive species can

eventually kill off the native species by eliminating their access to resources.

Other Effects on Resources

Let’s look at some of the natural and human-made conditions that can affect the resources available in

an ecosystem.

Disease

A disease can affect a species and decrease its population. As a result, resource availability for other

organisms may improve. However, the decline in the species’ population can decrease the availability of

food for predators that consume that species.

Selection

Genetic changes in a species can increase its likelihood of survival, causing its population to grow. As the

population rises, it can affect other species in the area. For example, sidewinder snakes are found in

deserts. Their color helps them to blend in with the sand. This coloration allows the snakes to conceal

themselves from predators and prey, increasing their chances of survival.

Natural Disasters

Floods, hurricanes, and other natural disasters can destroy resources such as food and shelter. They can

also kill populations of organisms. As a result, the chances of successful mating among these organisms

may decrease.

Human Activities

Activities such as clearing forest areas to build houses and constructing dams on a water supply can

reduce resources for plants and animals in the area.

The photograph shows a deforested area. Humans intentionally cleared the trees in this area for urban

development or to use the wood for lumber. How will this action affect the herbivores and predators

that live in the forest?

Careers in Science:

Population Ecologists

Ecologists study ecosystems and the interactions between organisms and their habitat. Population

ecologists specifically focus on factors that alter a population of organisms, either positively or

negatively. Population ecologists try to answer questions related to these factors:

Size of the population and its location in the ecosystem: For example, does the species live in one large

population in a small region? Does it have several smaller communities over a wide geographic range?

Births and deaths per year: How long do these animals live? What’s the number of adults and offspring?

On average, how many offspring survive to reproductive age?

Population growth rate: Is the population growing, shrinking, or stagnant? What are the factors

responsible for its growth rate?

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Population and Carrying Capacity

An ecosystem is an area where biotic factors interact with abiotic factors. The biodiversity of an area

indicates the variety of living species in that area. High biodiversity is a sign of a healthy ecosystem.

There should be a sufficient number of producers, consumers, and decomposers to have a balance in

the ecosystem. A sudden and uncontrollable increase or decrease in any of these organisms will affect

the other species in the system.

Organisms need resources from their environment, so they can sustain their population only if there’s

enough food, water, and shelter available. A population’s survival also depends on the population of

other organisms in the ecosystem, because all organisms compete for resources in an ecosystem.

Scientists can estimate the maximum number of organisms of a species that an ecosystem can hold. This

number is called the carrying capacity. To calculate carrying capacity, scientists also consider the

availability of nutrients and energy in the ecosystem needed by that particular species. Using different

methods, scientists can predict the carrying capacity and the effect of overpopulation of a species in a

particular ecosystem.

Overpopulation

Space is a major resource that all organisms, including humans, need. Some people live in big houses,

while some people share space with other people. Large families often share the same house. No matter

how big or small a person’s house is, every person needs some space to eat, sleep, and perform daily

activities. Similarly, other organisms also need space to perform their basic functions.

When scientists research population changes in an ecosystem, they first try to identify the amount of

space each organism requires to survive in its habitat. Every organism needs a particular amount of

space in its habitat. When the number of organisms in a space increases, they compete with each other

for resources such as food, water, shelter, and nesting areas.

Overpopulation occurs when the number of organisms of a species exceeds the ecosystem’s carrying

capacity. Overpopulation leads to a shortage of resources because there are more organisms competing

for a specific resource. For example, if 100 foxes live in a forest, they have the resources of the entire

forest for themselves. If 50 more foxes enter, there will now be 150 foxes needing the same forest

resources. If the forest can’t sustain this increase, then the original 100 foxes will have to comp ete with

the new foxes for food and shelter.

Draw a line graph of the squirrel population data from year 1 to year 10.

What trend can you observe in the population of squirrels based on the graph you created in part A?

Factors That Affect Biodiversity

Diversity in an ecosystem is a result of interactions between different communities and factors. Species

depend on one another for their survival. A change in the population of one species affects the

population of other species in the ecosystem. As a result, scientists look at biodiversity to determine the

health of ecosystems.

Highly diverse ecosystems have different types of producers, consumers, and decomposers. It’s

important for the ecosystem to have enough species to provide it with variety and to support

environmental changes. For example, if there are plenty of species of insects for the birds in an

ecosystem to eat, then a change in the population of one of the insect species probably won’t have a

significant effect on the birds’ diets. But if there is only one species of insect for the birds to eat, then a

change in the insect population will have a greater effect on the birds.

Deforestation is the act of destroying forests so the land can be used for other purposes. Do you think

deforestation increases, decreases, or has no effect on the biodiversity of the forest ecosystem? Explain

your answer.

Many natural and artificial factors threaten the amount of biodiversity in an ecosystem. Let’s look at

some of these factors.

Exploitation of Resources or Organisms

Humans exploit natural resources for their own benefit. Clearing forests and pastures for agriculture

destroys resources that organisms in an ecosystem require. It also destroys the trees in that region and

reduces the fertility of the soil. People also tend to remove some animal species from their natural

habitat for their own needs. People keep these animals as pets or as sources of food. They also use

products that the animals make. These actions can cause the species to decline and can ultimately

damage the ecosystem. For example, excessive fishing in a small aquatic ecosystem may reduce the

number of fish in that ecosystem that other species depend on for food or for other resources.

Habitat Loss

Every organism has its own specific habitat. An organism depends on its habitat for food, shelter, and

other basic necessities. A loss of habitat will lead to a lack of space for the organism. Natural disasters

such as floods, earthquakes, and forest fires destroy the environment. Human activities such as

polluting, mining, and industrialization also reduce the space available in a habitat. The construction of

dams damages both land and aquatic ecosystems. Once their habitat shrinks, the organisms have

nowhere to go. Some organisms prey on human settlements. Loss of habitat is one of the major reasons

for reduction in biodiversity.

Climate Change

Climate plays an important role in maintaining the diversity of ecosystems. A change in climate could

affect an organism’s ability to adapt and survive in a new environment. The burning of fossil fuels leads

to an increase in the production of greenhouse gases. Carbon dioxide, a greenhouse gas, absorbs heat

energy from the sun, making the planet warmer. As a result, sea levels rise and rain cycles change,

affecting plants and animals. Watch the video on the next screen to learn how climate change affects

ecosystems and their biodiversity.

Climate change may cause the populations of some species to increase and expand their range of

distribution. Explain why this change can be positive for the species but negative for the ecosystems it

invades.

Symbiosis and Pollution

Pollution is the addition of unwanted substances in an environment. Excessive amounts of these

substances harm organisms and damage the balance of an ecosystem. Natural factors and human

activities cause pollution. Floodwaters carry substances from one place to another, leading to the

deposition of unwanted substances on land. Human activities include oil spills and chemical gases

leaking out into the atmosphere. These activities contribute to environmental damage. Damage to the

habitat and resources causes a decline in the number of organisms.

Interactions within ecosystems are interdependent and complex. A slight change in the number of

producers, consumers, or decomposers affects an ecosystem’s food web. In symbiotic relationships,

parasites harm their host. However, some parasites may also offer some surprising benefits to

organisms that live in polluted areas. Let’s learn more about these benefits.

Being infected with a parasite is usually not good news. These critters live in or on another. And they can

sicken or even kill their hosts. When an animal has to deal with both a parasite and pollution, these

stressors can add up. But that isn’t true for Artemia brine shrimp, a new study finds. Infection with

parasitic worms actually boosts the ability of these animals to survive in water laced with toxic arsenic.

Marta Sánchez works for the Spanish National Research Council in Seville. As an ecologist, she is

interested in how living things relate to one another and to their environment. She studies the role of

parasites. Her team was curious about brine shrimp because they are key players in their ecosystem.

(That term refers to the collection of plants, animals and other things that live nearby.) Brine shrimp are

crustaceans (Krus-TAY-shuns). They are eaten by many waterbirds, including flamingos. And those brine

shrimp can ferry pollutants and parasites into the birds.

When brine shrimp are infected by parasites called tapeworms, they turn red. This makes them easy for

birds to see. It also makes it easy for scientists to pick out the brine shrimp infected with worms..

And that’s what Sánchez and her colleagues did.

They collected brine shrimp from the area where the Odiel and Tinto rivers in southwest Spain join

before running into the Atlantic Ocean. Mining activities have tainted these waters with arsenic and

toxic heavy metals. All of these elements are considered pollutants.

In the lab, the researchers separated brine shrimp into two groups. Some were infected with

tapeworms; others were not. Then the scientists ran tests to see how well the tiny animals survived in

polluted water.

As the level of arsenic in the water increased, so did the number of brine shrimp that died. But brine

shrimp that were infected with worms survived better than uninfected ones did.

The researchers then ran their tests again. They were curious about how climate change might affect

the brine shrimp’s survival in polluted water. So this time they used warmer water. Again, worm

infection seemed to protect the brine shrimp from the effects of arsenic.

It may seem strange that parasites would protect an animal’s health. But causing its host to die quickly is

not good for a parasite. It needs its host to stay alive long enough for the stowaway to reproduce and

then move on to a new host. If that first host dies too quickly, so will the parasite. So helping brine

shrimp survive polluted waters may be in the worms’ best interest.

The worms may be helping to changing how their hosts deal with pollution and the stress it can cause.

When the researchers compared infected and uninfected brine shrimp, they found differences. Infected

brine shrimp had more droplets of lipids — fats — in their tissues. The lipid droplets may help the brine

shrimp sock arsenic away so that it can’t harm them.

Infected brine shrimp also produced more antioxidants. These are chemicals that protect an organism

from the damaging effects of stress on cells. Stressors can include things like exposure to poisons. In the

brine shrimp, “Infected individuals were better than uninfected individuals at coping under polluted

conditions,” Sánchez reports.

His team cannot say whether the beneficial link between tapeworms and brine shrimp is special to this

spot in Spain. “What we can say,” Sánchez notes, is that the reddening of organisms infected with

tapeworms has been seen at sites in other countries. For that reason, she suspects brine shrimp in other

places would show similar effects.

Power Words

antioxidant Any of many chemicals that can shut down oxidation — a biologically damaging reaction.

They do this by donating an electron to a free radical (a reactive molecular fragment) without becoming

unstable. Many plant-based foods are good sources of natural antioxidants, including vitamins C and E.

arsenic A highly poisonous metallic element. It occurs in three chemically different forms, which also

vary by color (yellow, black and gray). The brittle, crystalline (gray) form is the most common. Some

manufacturers tap its toxicity by adding it to insecticides.

brine shrimp Water-dwelling crustraceans in the genus Artemia. Some breeds of brine shrimp are sold

as novelty items known as “sea monkeys.”

cell The smallest structural and functional unit of an organism. Typically too small to see with the

naked eye, it consists of watery fluid surrounded by a membrane or wall. Animals are made of anywhere

from thousands to trillions of cells, depending on their size.

climate change Long-term, significant change in the climate of Earth. It can happen naturally or in

response to human activities, including the burning of fossil fuels and clearing of forests.

crustaceans Hard-shelled water-dwelling animals including lobsters, crabs and shrimp.

ecology A branch of biology that deals with the relations of organisms to one another and to their

physical surroundings. A scientist who works in this field is called an ecologist.

ecosystem A group of interacting living organisms — including microorganisms, plants and animals —

and their physical environment within a particular climate. Examples include tropical reefs, rainforests,

alpine meadows and polar tundra.

element (in chemistry) Each of more than one hundred substances for which the smallest unit of each

is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.

environment The sum of all of the things that exist around some organism or the process and the

condition those things create for that organism or process. Environment may refer to the weather and

ecosystem in which some animal lives, or, perhaps, the temperature, humidity and placement of

components in some electronics system or product.

host (in biology and medicine) The organism in which another lives. Humans may be a temporary host

for food-poisoning germs or other infective agents.

infection A disease that can spread from one organism to another.

lipid A type of fat.

molecule An electrically neutral group of atoms that represents the smallest possible amount of a

chemical compound. Molecules can be made of single types of atoms or of different types. For example,

the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and

one oxygen atom (H2O).

parasite An organism that gets benefits from another species, called a host, but doesn’t provide it any

benefits. Classic examples of parasites include ticks, fleas and tapeworms.

pathogen An organism that causes disease.

pigment A material, like the natural colorings in skin, that alter the light reflected off of an object or

transmitted through it. The overall color of a pigment typically depends on which wavelengths of visible

light it absorbs and which ones it reflects. For example, a red pigment tends to reflect red wavelengths

of light very well and typically absorbs other colors. Pigment also is the term for chemicals that

manufacturers use to tint paint.

pollutant A substance that taints something — such as the air, water, our bodies or products. Some

pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light.

Even weeds and other invasive species can be considered a type of biological pollution.

stress (in biology) A factor, such as unusual temperatures, moisture or pollution, that affects the health

of a species or ecosystem. (in psychology) A mental, physical, emotional, or behavioral reaction to an

event or circumstance, or stressor, that disturbs a person or animal’s usual state of being or places

increased demands on a person or animal; psychological stress can be either positive or negative.

tapeworm A type of parasitic worm that infects people and other vertebrate animals. These host

animals can become infected if they drink water or eat food that contains tapeworm eggs or larvae.

Ingesting tapeworm eggs can lead to infection in body tissues and organs. This can cause serious illness.

Adult tapeworms, which develop after an organism injects tapeworm larvae (not eggs), l ive in the

intestines of their hosts. They have long, ribbonlike bodies. Intestinal tapeworm infections can last for

many years, usually causing only mild symptoms.

tissue Any of the distinct types of material, comprised of cells, which make up animals, plants or fungi.

Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs

of the human body, for instance, often are made from many different types of tissues. And brain tissue

will be very different from bone or heart tissue.

toxic Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by

such a poison is its toxicity.

waterbird A bird that lives in or near water.

Why are tapeworms parasites to brine shrimps?

How does the tapeworm’s action inside the shrimp increase its chances of survival?

Scientists have observed unusual “benefits” of parasites in other species. This observation has led to

some scientific debate regarding whether some relationships that were once considered parasitic may,

in fact, be more mutualistic. Does the article support the idea of the existence of a mutualistic

relationship between tapeworms and brine shrimps? Explain your answer using evidence from the text.

Sort the activities above based on whether they decrease or maintain biodiversity.

These three organisms are interdependent on each other for their survival. What will happen if foxes are

eliminated from the region?

The dumping of garbage caused the population of crabs in an area to drop from 2,000 to 500. Crabs eat

algae and are preyed on by larger fish. How will the crab’s population change affect these two species?

Barrels containing toxic waste that were dumped into a body of water. What is the likely effect of the

dumping on this ecosystem?

Introduction

Oceans are vast expanses of saline water that cover about 70 percent of Earth’s surface. Oceans

contribute extensively to Earth’s biodiversity because many species of plants, animals, and microbes live

in oceans. Humans use many oceanic resources in our daily lives. However, pollution has contributed to

the destruction of oceanic biodiversity.

People often harm ecosystems, but some people are making good progress toward preserving

ecosystems. Read these questions related to ecosystems

What are some ways people help the environment?

Some conservation groups breed populations of endangered animals in captivity and then release them

into the wild. How does the reintroduction of animals affect the ecosystem? What factors should

conservationists consider before taking these actions?

Monitoring Biodiversity

Major events such as natural disasters cause significant changes in ecosystems that are clearly visible.

Other changes are so gradual that scientists can’t detect them without careful monitoring over time. In

these cases, various techniques help scientists recognize whether there’s a change in the biodiversity of

an ecosystem. Let’s investigate some of these techniques.

Components of Biodiversity

Scientists use various factors to measure the biodiversity of an ecosystem, including richness and

evenness.

Richness is the number of species present in an area. Various factors, including an area’s size, can cause

richness to vary widely. So, a large area will usual ly have more richness than a small one. Scientists can

use the richness of a sample and the size of the sample area to estimate the number of species that exist

in the ecosystem.

Evenness is the measure of the relative proportion of the different species i n a given area. When one

species is significantly higher or lower in number than other species in the area, the ecosystem is said to

have low evenness. When the species are balanced, the ecosystem has high evenness.

Scientists study the distribution of species in an area and can detect these aspects:

A change in balance: Scientists can detect an imbalance in the number of predators and prey, or in the

number of producers and consumers.

A change in abiotic factors: A change in abiotic factors is very evident during natural disasters and long-

term environmental changes. For example, higher temperatures might increase the populations of

certain pathogens, causing other species to die out faster because of diseases.

New species: If scientists detect a new species that they didn’t collect in earlier samples, it could indicate

a change in the ecosystem. Or the species could be a native species that has just changed its range.

Other times, detection of a new species can mean an invasive species has entered the area.

Preserving Biodiversity

An ecosystem with high biodiversity tends to be more stable than one that has lower biodiversity. This

increased stability is the reason many scientists have made conservation of ecosystems a priority. One

example is in the Maldives, an island nation in south Asia. The Maldives government has undertaken a

project that aims to improve and protect the coral cover.

Conservation Efforts

Conservationists use various techniques to protect ecosystems. A technique that works for one

ecosystem may not work for another. So, conservation techniques are usually specific to a particular

ecosystem. Scientists also have to consider the pros and cons of every method and determine whether

the advantages outweigh any potential negative effects.

Often, conservationists require the participation and support of politicians, citizens, and scientists to

make their efforts successful. Here are some steps that conservationists take to improve ecosystems:

Making laws: Conservationists work with lawmakers to introduce laws that can help prevent the

destruction of natural habitats.

Regulating or banning exploitive behaviors: To protect endangered plants and animals, conservationists

regulate acts such as hunting, poaching, and cutting down trees.

Purifying water: Conservationists purify water to remove harmful chemicals. Their actions provide

ecosystems with clean water.

Preventing soil erosion: Wind and water can carry soil from one place to another, resulting in soil

erosion. Soil erosion causes a decrease in fertile soil. To limit soil erosion, conservationists try to divert

water flow and plant more trees.

Raising endangered species in protected areas: Conservationists breed and raise endangered species in

wildlife sanctuaries and zoos. Some of these places have programs that aim to increase the population

of these species in the wild.

Restoring damaged areas: Conservationists work to restore damaged areas. One example is

reforestation. Conservationists plant new trees in areas where deforestation has taken place.

In addition to these efforts by conservationists, citizens can also help to improve ecosystems.

What are some ways people help the environment?

Some conservation groups breed populations of endangered animals in captivity and then release them

into the wild. How does the reintroduction of animals affect the ecosystem? What factors should

conservationists consider before taking these actions?

A local politician says the government shouldn’t waste money on reforestation because it doesn’t work.

To support his claims, he uses this graph, which shows the trend of deforestation and reforestation in

Africa, South America, and Asia. Why doesn’t this graph strongly support his argument?

An ecosystem is shown in the illustration. Assume that human activities have led to a decrease in the

number of eagles. A virus attack on rabbits has led to a decrease in their population in the ecosystem.

Which two sentences describe likely effects on the ecosystem?