7 4 EVIDENCE OF EVOLUTION evolution unit OVERVIEW

7. 4 EVIDENCE OF EVOLUTION evolution unit

OVERVIEW OF EVOLUTIONARY EVIDENCE Transitional Fossils Biogeography Embryology Analogous vs Homologous Features Vestigial Features

TRANSITIONAL FOSSILS If current species are descended from fossilized ancestors, we expect intermediates in the fossil record. The "walking whale" example from the video, or the archaeopteryx example to the right linking modern birds with dinosaurs.

BIOGEOGRAPHY The scientific study of the geographic distribution of organisms based on both living species and fossils. Many islands, such as New Zealand, Hawaii, and the Galapagos, have species of flightless birds that appear very related to species of birds from nearby mainlands that can still fly.

Observations from the Galapagos Islands Darwin’s hypotheses regarding remote islands Many species of plants, birds insects, and, Only these kinds of organisms are able to reach in some cases reptiles remote islands by crossing large expanses of open ocean No native amphibians and very few land mammals Amphibians and most mammals are unable to cross open ocean and will not be found in remote islands Many unique species found nowhere else on Earth Over time, ancestral species have evolved into new geographically isolated species Unique species most closely resemble species on the nearest continental land mass Unique species are descendents of ancestral species from the nearest continental land masses and will exhibit some similarities

Homologous Feature: A structure with a common evolutionary origin that may serve different functions in modern species (for example, bat wing and human arm).

EMBRYOLOGY The study of early, prebirth stages of embryonic development. All vertebrate embryos have pharyngeal slits that eventually form into gills in fish but disappear from land-based vertebrate.

Analogous Feature: A structure that performs the same function as a another but is not similar in origin or anatomical structure; for example, bird and insect wings.

VESTIGIAL FEATURES A non-functioning, or mostly non-functioning, structure that is homologous to a fully functioning structure in closely related species.