Introduction to Ecology

Lesson outcomes define ecology and ecosystem distinguish between biotic factors and abiotic factors and describe examples to illustrate each explain how abiotic factors affect the sustainability of the ecosystem describe examples to illustrate biotic interactions describe ways that organisms respond to changes in environmental conditions describe symbiotic relationships including: mutualism, commensalism, parasitism, and predation describe trophic structure in terms of food chains and food webs explain how biotic and abiotic factors affect ecological interactions and the distribution of organisms

Ecology is the scientific study of the interactions of organisms and their environment. Interactions of organisms and their environment refers to the way the organism affects the environment as well as how the environment affects the organism.

An Ecosystem is a community of organisms and the physical environment in which it lives.

Each of the following concepts describes the organisms within their environment Abiotic Factors Biotic Factors Symbiotic Relationships Trophic Structure Herbivore, Carnivore, Omnivore and Saprobes

Abiotic Factors Abiotic factors are the nonliving factors which affect life in any ecosystem. Some abiotic factors are described below: Space Temperature Oxygen Sunlight Water Inorganic and Organic Soil Nutrients

Biotic Factors Biotic factors refer to the living environment and include all other organisms that interact with the individual both of the same species and all other species.

Biotic factors also includes: Detritus (decomposing animals and plants) and Disease Predator/prey interaction Competition Symbiotic relationships

Symbiotic relationships Symbiotic relationships are biotic relationships in which two different organisms live in close association with each other to the benefit of at least one. There are five types of symbiotic relationships including: mutualism, commensalism, parasitism, parisitoidism. and predation.

Symbiotic relationships Mutualism is the type of symbiosis resulting in mutual benefit to both of the organisms in the relationship. An example of this would be the relationship between the algae and fungus of lichens. The fungi penetrate the roots of the plants and make soil nitrogen available to the plant, receiving carbohydrates in return. This allows them to live in an environment in which neither could survive alone.

Symbiotic relationships Commensalism is a relationship in which one organism benefits from the relationship but the other organism seems to neither be harmed nor benefited. One example to illustrate commensalism is the beaver and the fish. A beaver builds a dam to regulate water level which helps the beaver survive winter. The fish benefit from the beaver, but the beaver is neither harmed nor gains benefit from the fish. Another example of commensalism is the relationship between trees and nesting birds.

Symbiotic relationships Parasitism is a symbiotic relationship in which one organism benefits and the other is harmed. The organism that benefits is called the parasite, the organism that is harmed is called the host. An example would be the tapeworm. They live in the digestive tracts of various organisms, while there they are provided with nutrient and an environment in which to grow and reproduce. However, the host is harmed by the presence of the tapeworm.

Symbiotic relationships Predation is where the interaction is beneficial to one species and detrimental to the other. This is not always considered a symbiotic relationship, although it is quite similar to parasitism, except for the degree of harm to the host or prey. With predation, the prey is killed. An example of predation is when a lion kills a zebra and eats it as its source of food.

Trophic Structure Trophic structure refers to the feeding relationships within the ecosystem. These feeding relationships are generally divided into five trophic levels based on their source of nutrition

Trophic Structure Five trophic levels based on their source of nutrition primary producers primary consumers secondary consumers tertiary consumers decomposers (also known as detritivores).

Trophic Structure Feeding relationships are generally viewed as a food web consisting of all the possible food chains that exist within the ecosystem.

Trophic Structure Producers or autotrophs are organisms, such as green plants, that produce their own food. They make organic compounds (food such as sugar) from inorganic compounds (carbon dioxide and water) by photosynthesis. Consumers or  heterotrophs are organisms that obtain nutrients from other organisms. They cannot synthesize their own food so they must obtain it ready made.

Trophic Structure Decomposers are organisms of decay. These are also called saprobes. They are generally fungi or bacteria that break down the complex compounds in the remains of dead animals and plants, producing simple substances that can be used again by the producers.

Trophic Structure Herbivores are animals that feed only on plants. Rabbits, cattle, horses, sheep and deer are all herbivores. Carnivores are animals that feed on other animals. Some carnivores may be predators (such as lions, hawks, and wolves who attack and kill their prey and feed on their bodies) and some may be scavengers (they feed on dead animals that they find). Omnivores are animals that feed on both plants and animals. Examples of omnivores are humans and bears. Saprobes are organisms that get nutrients by breaking down the remains of dead plants and animals, or their wastes. Examples of saprobes are bacteria and fungi.

1. Which branch of biology studies the interactions among organisms and their environment? a. meteorology b. ecology c. botany d. genetics 2. Which is an example of a biotic factor that affects the size of a population in a specific ecosystem? a. average temperature b. amount and kinds of soil minerals c. concentration of oxygen d. number and kinds of predators 3. Which is the best example of a biotic interaction? a. Plants grow more slowly in winter than in summer. b. Fish move to deeper, cooler water during summer. c. Sea birds often compete for nesting space. d. Wind often causes trees to grow very short. 4. Fish often live in a beaver pond. What relationship is illustrated by this example? a. mutualism b. commensalism c. parasitism d. predation 5. Which term refers to an animal, such as a bear, that eats both plant and animal? a. autotroph b. primary consumer c. herbivore d. omnivore 6. Which is required by any terrestrial ecosystem? a. a producer b. a tertiary consumer c. at least five trophic levels d. a fourth level carnivore

1. Which branch of biology studies the interactions among organisms and their environment? a. meteorology b. ecology c. botany d. genetics 2. Which is an example of a biotic factor that affects the size of a population in a specific ecosystem? a. average temperature b. amount and kinds of soil minerals c. concentration of oxygen d. number and kinds of predators 3. Which is the best example of a biotic interaction? a. Plants grow more slowly in winter than in summer. b. Fish move to deeper, cooler water during summer. c. Sea birds often compete for nesting space. d. Wind often causes trees to grow very short. 4. Fish often live in a beaver pond. What relationship is illustrated by this example? a. mutualism b. commensalism c. parasitism d. predation 5. Which term refers to an animal, such as a bear, that eats both plant and animal? a. autotroph b. primary consumer c. herbivore d. omnivore 6. Which is required by any terrestrial ecosystem? a. a producer b. a tertiary consumer c. at least five trophic levels d. a fourth level carnivore

Read 1.5 "Ecology" on pages 22-23. Answer questions 1-6 from "Understanding Concepts" on page 23.