Struggle to Survive
The ability to respond and adapt to changes in the environment is one of the most important characteristics of living things.
Living things must make both short term adjustments such as the temperature changes from day to night and long term changes such as the warming or cooling of the earth.
Short term changes occur quickly and easily with a change in behavior such as moving into the sun when it’s cold or the shade when its hot.
Long-term changes may require changes in the very nature of the species.
In the 1700's, geologists uncovered evidence ofchanges in the Earth's history. The fossil remains of organisms totally different from those that live today were found, such as the saber-toothed tiger, the wooly mammoth, and the dinosaurs.
Species that no longer exist are said to be extinct. Fossil evidence showed many species had become extinct over Earth's history. By the middle of the 19th century, evidence for a changing Earth was strong. The loss of species is a concern because species are interdependent and one affects another.
Interdependence
Organisms are tightly connected to the nonliving world and to each other.
Many of the roles that organisms play involve food. One such relationship involving food is the predator-prey relationship. A predator is an organism that kills and eats another organism. The animal that is eaten is called prey. If the predator population uses a new, more efficient way to catch the prey, then the prey population must develop new ways to avoid being caught.
Relationships in which different species depend upon each other are known as symbiosis. There are three types of symbiosis:
mutualism -- where both organisms benefit, such as the crab that carries sea anenomes in its claws. The crab gets protection from the anenomes stinging tentacles. The anemone gets leftover food when the crab feeds.
commensalism -- where on organism benefits and the other is unaffected, such as bromeliads growing on tree branches. The bromeliad gets better exposure to sunlight. The tree is not harmed.
parasitism -- where one organism (the parasite) benefits and the other organism (the host) is harmed, such as tracheal mites that live and breed in the tracheal tubes of honeybees, eventually obstructing their airways and killing them.
These types of relationships have evolved over millions of years and may be quite specialized.
A small change in one organism such as in its population size can have a major impact on all the other organisms in an environment.
Environmental Awareness
As part of the web of life, humans affect and are affected by the living things around them. Biology affects many aspects of everyday life, including food, shelter, and health