Biological Evolution Standard B – 5.1

Standard B-5 The student will demonstrate an understanding of biological evolution and the diversity of life. Indicator B – 5.1: Summarize the process of natural selection.

Key Concepts Biological evolution: microevolution, macroevolution Natural Selection Overproduction of offspring Variation: inherited traits Adaptation: fitness, survival of the fittest Descent with modification

What You Already Know! In the 6th grade, you summarized the basic function of the structures of animals that allow them to defend themselves, to move, and to obtain resources. In the 8th grade, you explained how biological adaptations of populations enhance their survival in a particular environment.

What You Should Understand After This Lesson What biological evolution is. The difference between microevolution and macroevolution. How biological evolution occurs because of natural selection. The 4 principles of natural selection.

Objective Compare microevolution and macroevolution. Summarize the process of natural selection. Explain how changes in the environment may result in the appearance or disappearance of particular traits.

Vocabulary biological evolution microevolution macroevolution natural selection variation adaptation heritability fitness gene pool population

What is Evolution? What do you think about when you hear the word evolution? Name some things (living or nonliving) that have changed over time. Let’s watch a video.

Charles Darwin Charles Darwin (2-12-1809) Developed the theory of evolution. Father of evolution Sailed around the world on a 5-yr. voyage aboard the HMS Beagle. Observed life and vegetation as well as collected specimens at every port to come up with his hypothesis about the way life changes over time.

Charles Darwin & Natural Selection The Galapagos Islands Of all of his stops, this was the most influential to the theory. Although the islands were close together, they had varying climates. The plants and animals varied from island to island as well. Collected many samples for further observation.

How do you Survive? Darwin concluded that in order to survive, organisms must be able to adapt to their environments. Environments are constantly undergoing change. If the organisms want to continue to live, they have to be able to respond to that change. Some can adapt more easily than others. This is called fitness. Those that survive, must be able to pass that adaptation on to the next generation. This is heritability.

Charles Darwin & Natural Selection Darwin realized that organisms struggle to survive. Compete for food, space, escaping from predators, finding a mate, locating shelter Only some organisms live long enough to produce offspring The Struggle for Existence Survival of the Fittest

Natural Variation Charles Darwin argued that natural variation is present in ALL organisms. Organisms vary in size, color, shape, biochemistry, physiology, etc.

Natural Selection Darwin explains natural selection. Happens in nature (no human intervention) Occurs when organisms with certain variations survive, reproduce, and pass their variations to the next generation. Organisms without these certain variations will die and NOT pass them on to their offspring.

4 Principles of Natural Selection Overproduction of Offspring Variation of Inherited Traits Adaptation Descent with Modification

Overproduction of Offspring The ability of an organism to have many offspring increases its chances of surviving. However, it also increases the completion for resources. Organisms tend to produce more offspring than can or will survive. Spider Eggs

Variation of Inherited Traits Within any population, variation exists among the inherited traits of the individuals. This variation refers to the phenotype, or physical trait, of the individual. This phenotype can allow an organism to better gain the resources they need in order to survive. These variations are controlled by both genes and the environment.

Adaptation Adaptations lead to the increase in frequency of a particular trait. With every generation, organisms with this favorable trait become more adapted to their environment. Those organisms without the favorable trait become less and less in the population. The gene pool of a population can change over time. The water spider can spend its entire life underwater. It only needs to come up once daily for oxygen. It has adapted to living in the water.

Descent with Modification As the environment of a population changes, the entire process of natural selection can yield populations with new phenotypes. Natural selection can produce populations with different phenotypes from their ancestors. As long as those successful traits are beneficial to the organism, they will continue to passed down.

Two Types of Evolution Microevolution Happens on a small scale. Within a single population. Macroevolution Happens on a large scale. Transcends the boundary of a single species.

Simulation Let’s look at a well-known example of natural selection: The Peppered Moth