HS+BIO+Life+Cycles+Lesson+3

In the previous lesson we discussed energy and how it can be used to create or perpetuate life. Can you tell me something you remember from our lesson on energy?

Today we will be discussing evolution, or how life changes. Our lesson will cover how evolution creates new species through variation. We will also explore the relationships that living things have with their surroundings. The lesson will conclude with a brief review.

Life must change to grow.



Dinosaurs once existed on Earth, although we don't see these big lizards on the planet today. Dinosaurs are one of many examples that show biologists that life changes.



The process of life changing over time is called evolution.

The actions of evolution happens in cycles, but the products are different.

Scientists groups all organisms into species.



Individuals in the same species can reproduce with each other. Life changes over time by creating new species, a process called speciation.





Speciation usually happens in bursts. When a species becomes extinct (or dies out), room is made in the habitat for a new species to grow. Usually new species have adaptations, or changes, that make them better able to live in new areas. As these new species grow, some are better able to live than others.

Can you think of a common animal has some type of variation? (bears, dogs, cats)





At some point, a major event (like an earthquake or flood) will happen to cause a species to become extinct. When this happens, speciation starts over again. Evolutionary cycles are very gradual and happen over millions of years. Life must change, or evolve, to grow.



Environments are a main cause of evolution. The environment is an organism's natural and man-made surroundings.



Life uses energy to grow and change over time, or evolve. Ecology is a branch of biology that studies the relationships of living things with each other and their surroundings, and looks at how members of the same or different species live together.

The environment has its own cycles that keep everyday life going.



Ecosystems are made up of all the living things in a particular area. In this picture, the frog and the lilies are living things. The water is a non-living thing. A biologist may study why a frog lives in this pond.

Can you point to something else that is living?

Ecologists also study the behavior of organisms and how their environment, or changes in their environment, can cause them to act a certain way.



Organisms' behavior often occurs in cycles. For example, birds fly south for the winter. Then fly north in the spring.

Chipmunks, woodchucks, box turtles, and toads go into hibernation during the summer.



As spring approaches, they become active. The way the body sends a message is in a cycle. Some cycles happen in less than a second, like body messages. Other cycles take years to run a full coarse.