Bellwork: Pull out Natural Selection Lab Summary for me to read. Work on Butterflies

What is Evolution? Natural Selection Evidence for Evolution

Evidence for Evolution The degree to which species are related depends on how closely in time they diverged, or split, from their common ancestor. Evidence for Evolution comes from 6 areas Lesson 3-1

1. Fossils Although the fossil record is incomplete, it contains many examples of fossil sequences showing close ancestral relationships. Lesson 3-1

The fossil record indicates that different species of similar organisms often overlapped with each other. EX: Horses Lesson 3-1

Comparative Anatomy Comparative anatomy is the study of similarities and differences among structures of living species. By comparing anatomy of different species, scientists are able to find clues as to how organisms are related. Lesson 3-1

2. Homologous Structures Homologous structures are body parts of organisms that are similar in structure and position but different in function. Lesson 3-1

The forelimbs of these species are different sizes, but their placement and structure suggest common ancestry. Lesson 3-1

Evidence for Evolution (cont.) How do homologous structures provide evidence for evolution? Lesson 3-1

3. Analogous Structures Body parts that perform a similar function but differ in structure are analogous structures. Lesson 3-1

It illustrates that organisms can change over time. These structures developed independently of one another. They are made of different materials and have different structures, however, both fly. These organisms did not have a common ancestor with wings, but both developed wings over time. It illustrates that organisms can change over time. Lesson 3-1

4. Vestigial Structures Vestigial structures are body parts that have lost their original function through evolution. Lesson 3-1

The presence of these structures suggest that they once used them, but have changed so they no longer need them. If they did not need these structures at one point in their evolutionary past, then why have them? Lesson 3-1

Evidence for Evolution (cont.) How are vestigial structures evidence of descent from ancestral species? Lesson 3-1

5. Embryology The science of the development of embryos from fertilization to birth is called embryology. embryology from Greek embryon, means “to swell” and from Greek logia, means “study of” Lesson 3-1

The remarkable similarity among with similar structures that not all exhibit as adults suggests they once had a common ancestor. Lesson 3-1

Evidence for Evolution (cont.) How do pharyngeal pouches provide evidence of relationships among species? Lesson 3-1

6. DNA Molecular biology is the study of gene structure and function. Discoveries in molecular biology have confirmed and extended much of the data already collected about the theory of evolution. Scientists can study relatedness of organisms by comparing genes and proteins among living species. Lesson 3-1

Evidence for Evolution (cont.) How is molecular biology used to determine relationships among species? Lesson 3-1

Evidence for Evolution (cont.) Scientists have found that some stretches of shared DNA mutate at regular, predictable rates. Scientists use this “molecular clock” to estimate at what time in the past living species diverged from common ancestors. Lesson 3-1

Molecular data indicate that whales and porpoises are more closely related to hippopotamuses than they are to any other living species. Lesson 3-1

The Study of Evolution Today New evidence supporting the theory of evolution by natural selection is discovered nearly every day, but scientists debate some of the details. New fossils that have features of species that lived both before them and after them help scientists study more details about the origin of new species. Lesson 3-2

Many scientists think that natural selection produces new species slowly and steadily. Other scientists think species exist stably for long periods, and change occurs in short bursts. Lesson 3-2