What is one method of establishing the age of rocks and sediments on Earth?

1. What is one method of establishing the age of rocks and sediments on Earth? Radioactive dating

2. What is an isotope? Isotopes are atoms of the same element that differ in the number of neutrons they contain.

3. What makes an isotope unstable? An unstable isotope has nuclei that tend to release particles, or energy, or both. These are called radioactive isotopes.

4. What is “half-life?” The half-life is the amount of time it takes for one-half of a sample of isotope to decay.

5. What is the unstable isotope of carbon? Carbon-14

6. What is a mass extinction? During a mass extinction, large numbers of species become extinct throughout the Earth. How many mass extinctions are recorded in the fossil record? Five

7. What impact do mass extinctions have upon the life on Earth? Many habitats and niches are made available as species become extinct. This paves the way for the evolution of many new species.

8. What are homologous structures? Homologous structures are structures that are similar in structure but are different in function.

9. Give an example of a homologous structure. Example: the wing of a bat, the flipper of a whale, the foreleg of a cat, and the arm of a human. These animals show the same arrangement of bones from the shoulder to the tips of the digits, even those these appendages have very different functions. It is unlikely that the same arrangement of bone appeared independently in each of these groups. It is more likely that this structural “theme” was present in a common ancestor.

10. What are analogous structures? Analogous structures are structures that have similar functions, but are very different in structure.

11. What evolutionary trend is shown with homologous structures? Analogous structures? Homologous structures show evidence of kinship. Two organisms that share homologous structures are closely related. Analogous structures show that two organisms found similar solutions to similar problems. These organisms are not closely related to one another.

12. What are vestigial structures? Vestigial structures are body parts that are reduced in size and seem to be left over from a previous ancestor. These are historical remnants of structures that had important functions in the past.

13. What are embryological homologies? A comparison of early embryological structures reveals structures that are found in embryos of related organisms. All vertebrate embryos have structures called pharyngeal gill slits in their throat regions and a postanal tail at some point during their development.

14. What are homologous genes? Genes that are inherited from a common ancestor. All types of green plants have similar chlorophyll genes. Example: Cow CTATG Deer CTATG Whale CTATC Hippo CTATC

15. What is biogeography? Biogeography is the study of the past and present distribution of species.

16. What is a “gene pool?” Gene Pool: the sum total of all of the alleles of all of the genes of all the individuals in the population

17. What is a mutation? A mutation is a change in the nucleotide sequence of an organism’s DNA.

18. What is directional selection? Directional selection occurs when conditions favor individuals showing one extreme phenotype. This increases the gene frequency for the phenotype in one direction or the other. This type of selection is common when the environment changes or when members of a population migrate to new and different habitats.

19. What is disruptive selection? Disruptive solution occurs when conditions favor individuals at both phenotypic extremes at the expense of the intermediate forms.

20. What is stabilizing selection? This acts against both extreme phenotypes and favors the intermediate variants. This reduces variation in the population.

21. What are the two main types of sexual selection? Female choice Male vs Male Competition