Environmental Science

Life Science

 
Energy Flow Biodiversity Organism Relationships

Ms. Jennifer Smith

mailto: Smithj@plainfieldschools.org

Click here for homework site   http://assignaday.4teachers.org/   

Life Science is a biology course designed for juniors and seniors who have previously taken Biology, but are not in a college preparatory program.  Students will investigate the structure and function of the human body.  Throughout each unit students will study related areas such as drugs, alcohol and major diseases.  Research, critical thinking and laboratory skill are required to successfully complete this course.

 Environmental Science is a course for general level junior or seniors.  It is designed to integrate several science disciplines.  These include hydrology, meteorology, geology and biology.  Students in class will use a multidisciplinary approach to explore current topics affecting the environment around the world.  The course involves hands on activities, research and critical thinking.

Pictures of PHS students exploring science!

 

Parents, this site will help your child with specific questions on the CAPT science test.

http://www.state.ct.us/sde/dtl/curriculum/science/s5stshumanpopulationteacher.doc

 

Energy Flow

 

 

Feeding Relationships
Energy flows through ecosystems in one direction, typically from the Sun, through photosynthetic organisms including green plants and algae, to herbivores to carnivores and decomposers.  Green plants and algae are called autotrophs or producer organisms, as they capture solar energy to make sugars in the process of photosynthesis.   Herbivores or primary consumers use the producer organisms to provide them with their food.   Carnivores are secondary consumers as they eat the primary consumers as their source of food.    Some organisms are capable of functioning as primary consumers (eating plant material) and as secondary consumers (eating animal material).   These organisms are called omnivores.  Humans are examples of omnivores.   All consumers are examples of heterotrophic organisms, as they can not make their own food using the sun, but depend upon the ingestion of other organisms for their nutrition.

Food Chains
If an ecosystem is to be self-sustaining it must contain a flow of energy.   One way of  representing the flow of energy through the living components of an ecosystem is through the use of a food chain.   A food chain indicates the transfer of energy from producers through a series of organisms which feed upon each other.

A Food Chain

Note that the arrows in the food chain point to the organisms which are doing the eating.   Thus the arrows in the food chain represent the flow of energy through the ecosystem.

The algae and floating plants are the producers in this food chain.   The aquatic crustaceans are the primary consumers which eat the producers.

Fish are secondary consumers eating the primary consumers.

A food chain may also contain third level or other consumers as indicated by the raccoons in this food chain.

Food Webs
In a natural community, the flow of energy and materials is much more complicated than illustrated by any one food chain.   A food web is a series of interrelated food chains which provides a more accurate picture of the feeding relationships in an ecosystem, as more than one thing will usually eat a particular species.

A Food Web

Energy flow in a food web also starts with the producer organisms through the various levels of consumer organisms as in a food chain.   

Energy Pyramids
An energy pyramid provides a means of describing the feeding and energy relationships within a food chain or web.    Each step of an energy pyramid shows that some energy is stored in newly made structures of the organism which eats the preceding one.   The pyramid also shows that much of the energy is lost when one organism in a food chain eats another.   Most of this energy which is lost goes into the environment as heat energy.   While a continuous input of energy from sunlight keeps the process going, the height of energy pyramids (and therefore the length of food chains) is limited by this loss of energy.

An Energy Pyramid

The picture at the left is an energy pyramid.   Producer organisms represent the greatest amount of living tissue or biomass at the bottom of the pyramid.   The organisms which occupy the rest of the pyramid belong to the feeding levels indicated in each step.    On average, each feeding level only contains 10% of the energy as the one below it, with the energy that is lost mostly being transformed to heat. 

 

 

Biodiversity

 

 

Biodiversity
As a result of evolutionary processes, there is a diversity of organisms and a diversity of roles in ecosystems.  Biodiversity refers to the differences in living things in an ecosystem.  Increased biodiversity increases the stability of the ecosystem as it provides for more genetic variation among species.   A great diversity of species increases the chance that at least some living things will survive in the face of large changes in the environment.

The Need for Biodiversity

Human Influences on Biodiversity
When humans alter ecosystems either by removing specific organisms, serious consequences may result.   Human beings are part of the Earth’s ecosystems. Human activities can, deliberately or accidentally, change the equilibrium in ecosystems.  Humans are destroying other species as a result of population growth, consumption, and technology.   Human destruction of habitats through direct harvesting, pollution, atmospheric changes, and other factors is especially threatening current global biodiversity.

An example of a human activity which has decreased biodiversity is the use of monoculture in modern agricultural practices.   Monoculture involves planting one variety of a species over a huge area.   This leaves this area more vulnerable to predation or disease and the loss of many or all species.

Uses of Biodiversity
In addition to the aesthetic beauty added to the world by many different organisms, biodiversity also ensures the availability of a rich variety of genetic material that may lead to future agricultural or medical discoveries with significant value to humankind. As diversity is lost, potential sources of these materials may be lost with it.   

 

 

Organism Relationships

 

 

Feeding Relationships
Organisms may interact with one another in several ways.  One example of an organism interaction is that of a producer/consumer relationship.   A producer is any organism capable of making its own food, usually sugars by photosynthesis.   Plants and algae are examples of producers.   A consumer is any organism which eats another organism.   Several different types of consumer organisms exist.    A herbivore is a consumer which eats primarily plant material.  A deer is an example of a herbivore.   A carnivore consumes primarily animal material.   An omnivore eats both plant and animal matter.   Humans are examples of omnivorous organisms.

A predator is a type of carnivore that kills its food.   The organism the predator feeds upon is called its prey.    A wolf and rabbit would provide an example of a predator/prey relationship.    Scavengers feed upon organisms that other organisms have killed.    A crow feeding off dead carrion in the highway would be an example of scavenger in this instance. 

Scavengers Feeding

The cartoon above represents a typical situation where vultures are acting as scavengers feeding on a dead rhinoceros.

Symbiotic Relationships
Close living associations are called symbiotic relationships.  Parasitism is an example of such a relationship.   In this situation, the parasite feeds upon the tissues or fluids or another organism, but usually does not kill the organism it feeds upon, as this would destroy its food supply.   The organism the parasite feeds upon is called the host organism.  An example of this sort of relationship would be fleas on a dog or athlete's foot fungus on a human.

Types of Symbiosis
  • parasitism: the parasite benefits at the expense of the host
  • mutualism: both organisms benefit from the association
  • commensalism: one organism is benefited and the other is unharmed

Other Relationships
Some organisms such as certain pathogenic bacteria may cause disease in other organisms.  Decomposer organisms use the energy of dead organisms for food and break them down into materials which can be recycled for use by other organisms.   Bacteria of decay and many fungi are examples of decomposer organisms.

 

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