Chapter Seven: Evolution of Living Things
Chapter Seven: Evolution of Living Things
1. Biological Evolution explains how populations change over time.
2. When an organism blends into its environment it is camouflage.
3. A characteristic that helps an organism survive in its environment is called a/an adaptation.
4. An adaptation can be physical (fur color, presence of a long neck) or a behavior to help it attract a mate, get food, or protect itself) .
5. A group of organisms that can mate with each other to produce fertile offspring is called a species.
6. A population is a group of individuals of the same species.
7. Because the earth has changed gradually over time, living things have to change to adapt to their new environments. This gradual change in populations over time is called evolution.
8. Scientists theorize that as populations change over time, new species form.
9. Scientists have gathered evidence that change has occurred over time:
· Fossils- remains or imprints of once living organisms found in rock layers.
· By comparing characteristics and the order of existence of organisms in a time line called a fossil record.
· By drawing a tree of life (pg. 169), scientists can examine all known organisms and have hypothesized that all organisms have a common ancestor.
· Comparing traits (pg. 171) of animals have given scientist clues about their ancestors.
· Looking at DNA from different organisms has given scientists evidence that populations and species undergo changes in DNA and traits over time.
· Scientists have concluded that species that have a common ancestor will have traits and DNA more similar to each other than those of distantly related species.
10. Charles Darwin sailed around the earth for five years on a ship called the HMS Beagle as a naturalist – a scientist who studies nature. (Page 175 shows his journey)
11. Look at the illustrations of finches on page 175. Darwin observed that the birds on the Galapagos Islands were a little different than the finches in Ecuador, as well as each island having a little difference in finches. These differences were based on the way the finches obtained food.
12. Population growth activity (as explained in Mathus’s paper) that stated that food supplies could not support unlimited population growth.
ACTIVITY #1: Across your table in an imaginary block labeled “ food supply,” start by putting one bean in the first block, two in the second, three in the third, and continuing across the table by adding one additional bean per square for six squares.
Below these piles, in imaginary blocks labeled “human population,” start with block #1 and add bead. To the second block add two beads, and in the third block add four beads. Continue doubling the quantity of beads in each block as the previous block until you have six blocks.
What would happen to the food supply in this activity if the population continues to grow at this rate? The food supplies would diminish and the population would starve
What prevents this from happening with the human population? Human populations are limited by the choices they make or by problems such as starvation or disease
13. Darwin realized that the populations of all species are limited by such factors as starvation, disease, competition, and predation.
14. Darwin’s theory of natural selection is explained in the “On the Origin of Species” .Natural selection is the process by which organisms that are better adapted to their
environment survive and reproduce more successfully than those less well adapted organisms do. There are four elements to his theory.
State the four elements in your own words.
· A species produces more individuals than it needs. Some will develop into adults and others will not survive.
· Each individual has its own set of traits similar to but not identical to its parents
· Some individuals will not survive to adulthood. They will get eaten, starve, or die of disease.
· The adults that are most suited to their environment will reproduce offspring that are more likely to survive
15. Darwin’s lack of knowledge in how variation occurs is now understood by scientists; they now know that it happens as a result of differences in genes. This has led to further understanding of how evolution occurs.
16. Modern day evidence of natural selection in today’s world can be seen in bacteria. A few bacteria survive antibiotic treatment because they have an adaptation that makes them naturally resistant to the chemical and they survive and continue to reproduce. After several generations, you have a population of antibiotic resistant bacteria.
17. Read the section on page 180 and explain why there are more tuskless elephants now living in Uganda.
When the hunters killed off the long tusked elephants, the only elephants left to reproduce were short tusks elephants. Now there are more short tusked elephants than long.
18. Read page 181 and explain why insects quickly build up a resistance to pesticides.
Insect populations change quickly because they have a short generation time. The insects that are resistant to pesticides survive and reproduce insects that have this same trait.
19. Forming a new species is called speciation. This occurs when the new population and the original population vary so much they can no longer mate. Speciation may happen in several ways. List and explain below.
· Separation- when a part of a population separate from one another from events like canyon formation
· Adaptation- after two groups have separated, natural selection acts on each group differently giving them different traits.
· Division- after many generations, the two separated groups have enough differences they will no longer mate.
20. Habitat is the place an organism lives which provided food, shelter, and climate.
21. Niche is how something lives, eats, and survives in its ecosystem.
22. Mutations are an important source of new traits.
23. An organism can change over time through either gradualism or punctuated Equilibrium.
Read the two sections below and underline at least 2 important facts in each section.
Gradualism is selection and variation that happens more gradually. Over a short period of time it is hard to notice. Small variations that fit an organism slightly better to its environment are selected for: a few more individuals with more of the helpful trait survive, and a few more with less of the helpful trait die. Very gradually, over a long time, the population changes. Change is slow, constant, and consistent.
In punctuated equilibrium, change comes in spurts. There is a period of very little change, and then one or a few huge changes occur, often through mutations in the genes of a few individuals. Mutations are random changes in the DNA that are not inherited from the previous generation, but are passed on to generations that follow. Though mutations are often harmful, the mutations that result in punctuated equilibrium are very helpful to the individuals in their environments. Because these mutations are so different and so helpful to the survival of those that have them, the proportion of individuals in the population who have the mutation/trait and those who don't changes a lot over a very short period of time. The species changes very rapidly over a few generations, then settles down again to a period of little change.
24. Organisms adapt in a variety of ways to adapt to their environment: mimicry (the similarity in appearance of one species to another that protects one or both), camouflage, speed, particular physical features, etc.