Types of Interactions

1. Types of Interactions Pgs. 14 - 19

2. Interactions with the Environment • Most living things produce more offspring than will survive to adulthood. • For example, a female frog can lay hundreds of eggs in a small pond. • Within a few months the population of frogs in that pond will be about the same. Why? • The frogs interact with the biotic and abiotic factors within its environment to control the population size.

3. Limiting Factors • Populations of individuals cannot grow indefinitely. • The environment has a limited amount of food, water, living space and other needed resources. • When a resource becomes scarce it is a limiting factor. • Food is a limiting factor for large populations. • Any resource can be a limiting factor.

4. Carrying Capacity • The largest population that a given environment can support over a long period of time is known as carrying capacity. • If a population grows larger than its carrying capacity, limiting factors cause the population size to decrease. • Example: an environment has a very good growing season one year. The following year has a drought and poor growing season. The population eating the plants that grew, have less food the following year. Food will limit the population size.

5. Interactions Among Organisms • Populations contain interacting individuals of a single species in an area. • Communities, however, contain interacting populations of several species. • There are four main ways populations interact within an ecosystem: Competition, Predator-prey, Symbiotic relationships, and coevolution.

6. Competition • When two or more individuals or populations try to use the same limited resource such as food, water, shelter, space, or sunlight, it is called competition. • Competition can occur between individuals of one population or between populations of different species. • Elks in Yellowstone Park compete for plants to eat. • Different tree species compete for space(for their roots) and sunlight.

7. Predator and Prey • Prey is the organism that is eaten. • Predator is the organism that eats another organism. • To survive, predators have adaptations to help them catch their prey. • For example, cheetahs run fast, some spiders blend in with a prey’s food source, some can fly or swim fast. • Their adaptation allows them to catch their food better.

8. Prey Adaptations • Prey organisms have adaptations to help prevent them from being eaten. • Prey can run away, stay in groups, camouflage, have poisonous glands, or burrow underground. • Some animals can advertise their poisons with bright colors. • Groups of animals evade predators because there is always one or two individuals looking out for the group.

10. Symbiosis • A close, long-term association between two or more species is symbiosis. • Individuals involved in a symbiosis can benefit, be unaffected or harmed by the relationship. • The three groups of symbiosis we will discuss are mutualism, commensalism, and parasitism.

11. Mutualism (win,win) • A symbiotic relationship in which both organisms benefit is mutualism. • Humans have a species of bacteria in their intestines and both benefit. • The humans get vitamins that the bacteria produce and the bacteria get a food supply. • Another example is coral and algae. • The coral are a home for algae, and the algae produce food from photosynthesis that the corals use.

12. Commensalism (win, ehh) • A symbiotic relationship in which one organism benefits and the other is unaffected is called commensalism. • One example is sharks and remoras. • Remoras attach to sharks and feed on scraps of food left behind. • The remoras benefit and the sharks are unaffected.

13. Parasitism (win, lose) • A symbiotic relationship in which one organism benefits and the other is harmed is called a parasitism. • The parasite benefits, while the host is harmed. • Some parasites (ticks) can live on an organism’s body and some (tapeworm) live in the organism’s body. • One example is the tomato hornworm and wasps. • A female wasp will lay her eggs inside a hornworm. • When the eggs hatch, they eat the hornworm alive.

15. Coevolution • A long-term change that takes place in two species because of their close interactions with one another is coevolution. • Sometimes it occurs between herbivores and the plants they eat. • Example: Ants and Acacia. Ants attack herbivores that try to eat Acacia. Acacia produces food and an area for the ants to live. • They evolved together.

17. Coevolution and Flowers • Some flowers and their pollinators have coevolved as well. • The hummingbird coevolved with some flowers. • They have a long beak to reach into the flower for nectar. • As they reach in, they are smearing pollen from the plant on their head and will spread to the next flower they go to.