Science and Technology and Engineering: Ecology (Review)

Autotrophs, Producers, Herbivores, Carnivores, Omnivores, and Decomposers

Energy flows in one direction: from the sun, through photosynthetic organisms such as green plants (producers) and algae
(autotrophs), and then to herbivores, carnivores, and decomposers. Autotrophs are organisms capable of producing their own food. The organic molecules they produce are food for all other organisms (heterotrophs). Producers are green plants that manufacture food by photosynthesis. Herbivores are animals that eat only plants (deer, rabbits, etc.). Since they are the first animals to receive the energy captured by producers, herbivores are called primary consumers. Carnivores, or secondary consumers, are animals that eat the bodies of other animals for food. Predators (wolves, lions, etc.) kill other animals, while scavengers consume animals that are already dead from predation or natural causes (buzzards). Omnivores are animals that eat both plants and other animals (humans). Decomposers include saprophytic fungi and bacteria that break down the complex structures of the bodies of living things into simpler forms that can be used by other living things. This recycling process releases energy from organic molecules.

Abiotic Factors and Biotic Factors
Abiotic factors are the physical and chemical factors in the environment that are nonliving but upon which the growth and survival of living organisms depends. These factors can determine the types of plants and animals that will establish themselves and thrive in a particular area. Abiotic factors include:
Light intensity available for photosynthesis
Temperature range
Available moisture
Type of rock substratum
Type of minerals
Type of atmospheric gases
Relative acidity (pH) of the system
Biotic factors are the living components of the environment that affect, directly or indirectly, the ecology of an area, possibly limiting the type and number of resident species.
The relationships of predator/prey, producer/consumer, and parasite/host can define a community. Biotic factors include:
Population levels of each species
The food requirements of each species
The interactions between species
The wastes produced

How Plants Manufacture Food
Plants are the only organisms capable of transforming inorganic material from the environment into organic matter by using water and solar energy. This transformation is made possible by chloroplasts, flat structures inside plant cells. Chloroplasts, located primarily in leaves, contain chlorophyll (the pigment capable of absorbing light and storing it in chemical compounds), DNA, ribosomes, and numerous enzymes. Chloroplasts are surrounded by a membrane. The leaves of plants are the main producers of oxygen, which helps purify the air. The chlorophyll in chloroplasts is responsible for the light, or luminous, phase of photosynthesis. The energy it absorbs breaks down water absorbed through the roots into hydrogen and oxygen to form ATP molecules that store energy. In the dark phase, when the plant has no light, the energy molecules are used to attach carbon dioxide to water and form glucose, a sugar.

Producers, Consumers, and Decomposers
The food chain, or food web, is a series of events that happens when one organism consumes another to survive. Every organism is involved in dozens of connections with others, so what happens to one affects the environment of the others. In the food chain, there are three main categories:
Producers – Plants and vegetables are at the beginning of the food chain because they take energy from the sun and make food for themselves through photosynthesis. They are food sources for other organisms.
Consumers – There are three levels of consumers: the organisms that eat plants (primary consumers, or herbivores); the organisms that eat the primary consumers (secondary consumers, or carnivores); and, in some ecosystems, the organisms that eat both plants and animals (tertiary consumers, or omnivores).
Decomposers – These are the organisms that eat dead things or waste matter and return the nutrients to the soil, thus returning essential molecules to the producers and completing the cycle.

System of Classification for Living Organisms
The main characteristic by which living organisms are classified is the degree to which they are related, not the degree to which they resemble each other. The science of classification is called taxonomy. This classification is challenging since the division lines between groups is not always clear. Some animals have characteristics of two separate groups. The current system of taxonomy involves placing an organism into a domain (Bacteria, Archaea, and Eukarya), and then into a kingdom (Eubacteria, Archaeabacteria, Protista, Fungi, Plantae, and Animalia). The kingdoms are divided into phyla, then classes, then orders, then families, and finally genuses and species. For example, the family cat is in the domain of eukaryotes, the kingdom of animals, the phylum of chordates, the class of mammals, the order of carnivores, the family of felidae, and the genus of felis. All species of living beings can be identified with Latin scientific names that are assigned by the worldwide binomial system. The genus name comes first, and is followed by the name of the species. The family cat is felis domesticus.

Properties That Contribute to Earth's Life-Sustaining System
Life on earth is dependent on:
All three states of water – gas (water vapor), liquid, and solid (ice)
A variety of forms of carbon, the basis of life
(carbon-based units)
In the atmosphere, carbon dioxide, in the forms of methane and black carbon soot, produces the greenhouse effect that provides a habitable atmosphere.
The earth's atmosphere and electromagnetic field, which shield the surface from harmful radiation and allow useful radiation to go through.
The earth's relationship to the sun and the moon, which creates the four seasons and the cycles of plant and animal life.
The combination of water, carbon, and nutrients that provides sustenance for life and regulates the climate system in a habitable temperature range with non-toxic air.