Ecosystems Chapter 2:

2.1 Everything is Connected

• Scientists don’t yet completely understand how the environment works because it is so complex and interconnected

• Human actions have unexpected effects on the environment (ex: Borneo in Southeast Asia; pesticide DDT)

• The unfortunate chain of events on Borneo occured because the living things were connected to each other

What is an Ecosystem?

An ecosystem includes all the different organisms living in a certain area, along with their physical evironment (ex: coral reef, wetlands)

Ecologists think of an ecosystem as an isolated unit, but ecosystems usually do not have clear, cut boundaries; things move from one ecosystem to another (ex: birds fly from one ecosystem in summer to another in winter)

Ecosystems contain both biotic factors (living parts: animals, plants) and abiotic factors (nonliving parts: temperature, sunlight, soil type)

All parts work together in an ecosystem, if one part is destroyed, the entire ecosystem can be affected

Organism

An organism is one individual living thin)g (ex: an ant, an ivy plant, a gorilla)

A species is a group of organisms that are able to produce fertile offspring and share common genes, therefore, resemble each other (ex: all humans, domestic dogs)

Population

A population is a group of individuals of the same species living in a particular place (ex: the bullfrog population of a pond, the lion population of a savanna)

Community

Organisms don’t exist in isolation, neither does a population, every population is a part of a community

Communities are all the living inhabitants of interacting populations of different species living in an ecosystem (ex: a pond community includes the different plants, fish, insects, amphibians, microorganisms the live in and around the pond)

Niche and Habitat

Niche is an organism’s way of life (ex: a lion eats other animals (gazelle, zebra); the leftovers are consumed by scavengers (vultures, hyenas, bacteria, insects); the lion itself is also food to ticks, fleas, mosquitoes

An organism’s relationship with its environment, both the living and the nonliving

Niche includes when and how often it reproduces, how many offspring it has, what time of day it is most active, where it finds food; it’s “lifestyle”

Habitat is the actual place on organism lives (ex: lion’s habitat is a savanna, cactus’s habitat is a desert); it’s “address”

• Ecosystems are made up of biotic and abiotic components

• The biotic components – organisms – affect one another

• The five major types of interactions are: predation, competition, parasitism, mutualism and commensalism

2.2 How Species Interact with Each Other

Predation

In predation, one organism kills and eats another organism

The organism that is eaten is called the prey The organism doing the eating is called the predator Examples: lions feeding on zebras; cougars eating

deer; snakes consuming mice; birds eating insects; blue whale feeding on tiny krill

Predators tend to feed on young and weak individuals; as prey decline, predators either feed on other organisms or die

Competition

Competition occurs when two or more organisms of the same or different species attempt to use the same limited resource

Examples: Lions and hyenas fighting over the same carcass; two plants fighting for a limited amount of sunlight

Species can fight over the same resource and never see one another, ex: one insect feeding on a certain plant during the day and another who feeds on that same plant during the night; because they use the same food source, the two species are competitors

Parasitism

Parasites are organisms that live in or on another organism and feed on it without immediately killing it; parasitism is the relationship between the parasite and its host

Examples: ticks, fleas, tapeworms, viruses, blood-sucking leeches, mistletoe

Organism the parasite takes nourishment from is known as the host

The difference between parasitism and competition is that the parasite does not immediately kill their host; it lives in or on the host most of its life; and the parasite weakens its host making it more vulnerable for predators

Mutualism

Mutualism is the cooperative partnership between two species in which both species benefit

Examples: clownfish and the sea anemone; bacteria in your intestines; acacia tree covered in ants in Central America (when the ants were removed, the tree suffered)

Commensalism

Commensalism is the rarest and strangest type of species interaction

It is the relationship in which one species benefits and the other is neither harmed or helped

Example: sharks and remoras

Organisms tend to be well suited for their natural environment

Ex: Kangaroo rats are suited for areas with very little water (desert): never need to drink water, eliminate very little water, active at night

2.3: Adapting to the Environment

Evolution by Natural Selection

Scientists want to how the close match between organisms and their environment came about. Charles Darwin, 1859, proposed an answer. He observed that members of a population differ from each other in form, physiology and behavior; some differences are due to heredity (passed from generation to generation)

Environment influences which individuals have offspring; certain traits allow some individuals to survive and have offspring

Natural selection describes the unequal survival and reproduction from the presence or absence of particular traits; over the years, characteristics change over time

Evolution is a change in the genetic characteristics of a population from one generation to the next

Evolution by Natural Selection…con’t

Ex: a herd of deer live in lowland areas with warm climate; some become separated in the high mountains where the temperatures are cold most of the year; many die in the cold; the survivors might have thicker fur; they go on to reproduce with offspring having the desirable trait; this is an adaptation (an inherited trait that increases and organisms chance of survival and ability to reproduce)

Coevolution

An organism’s environment includes both the abiotic and the biotic aspects

When two or more species evolve in response to each other, it is called coevolution

Can be found between predator (enables them to find, subdue and capture prey) and prey (enables them to avoid, escape and fight off predators); ex: crabs (predator) and marine snails (prey); plants and herbivores

Extinction

The irreversible disappearance of a population or a species is called extinction

When the last individual of an organism dies, the species is considered extinct

This is a natural process but humans are causing species to disappear at an alarming rate