Textbook Notes (363,236)
Canada (158,278)
York University (12,359)
Biology (941)
BIOL 1001 (162)
Tamara Kelly (110)
Chapter 20

Chapter 20.docx

5 Pages
Unlock Document

York University
BIOL 1001
Tamara Kelly

Chapter 20 Darwin Fossils and Developmental Biology 2212012 75500 AM 206 Interpreting Evolutionary Lineages The earliest horses were small and stood at 2550 cm high walked on soft pads like dogs faces were short and ate leaves in woodland habitatsThe evolution of these horses caused them to run faster and change diet to tough grasses and live in open grasslands The evolution of horses had many branches and lineages but today only genus survives with many species including donkeys and zebras All evolutionary lineages have extinct branches so if we try to trace an evolutionary pathway based on comparisons of different and similar characteristics we will be creating an artificial pathway since we did not consider the extinct branches which may have related species that do not resemble the living species and had different evolution from the same ancestor Evolution can occur by gradual changes Anagenesis the accumulation of changes in a lineage as it adapts to changing environments It does not increase the number of species only transforms an existing species Cladogenesis the evolution of two or more descendant species from a common ancestor Increases the number of species on Earth The gradualist hypothesis suggests that large changes result from slow continuous accumulations of small changes over time Gradual fossil records are most often not found Usually you find fossils of one species and then it disappears and find fossil of the next in next stratum Punctuated equilibrium hypothesis suggests that speciation occurs in isolated populations at the edge of a species geographic distribution occurs rapidly If this hypothesis is correct then transitional fossil records are uncommon and the previous explanation is supported Data records support both hypotheses 207 Macroevolutionary trends in Morphology Body size affects most aspects of an organisms physiology and ecology Increases in body size are common but not universal this is called Copes rule when and organism increases body size over time Preadaptation occurs when a trait that is adaptive in one context is also advantageous in another These are lucky accidents no anticipation Eg Ancestors of birds were nonflying bipedals that had forelimbs to catch prey
More Less

Related notes for BIOL 1001

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.