sponge: set up cornell notes on pg. 51 topic: 5.4 evolution: evidence for evolution: fossil record...
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Sponge: Set up Cornell Notes on pg. 51
Topic: 5.4 Evolution: Evidence for Evolution: Fossil Record
Essential Question: Explain why the fossil record is one of the key pieces of evidence for the theory of evolution.
BIOZONE: 238-251 due 11/05
5.4 Evolution: Evidence for Evolution
Key Vocabulary:Fossil RecordHomologous StructuresEmbryology
Explain why the fossil record is one of the key pieces of evidence for the theory of evolution.
BIOZONE: 238-251 due 11/05
Assessment Statement
• 5.4.2 Outline the evidence for evolution provided by the fossil record, selective breeding of domesticated animals and homologous structures
Evidence for EvolutionMajor pieces of evidence for evolution
• Artificial Selection• Fossil Record• Homologous Anatomical Structures• Embryology
Fossil Record• The fossil record gives scientists clues about what life was like millions of
years ago• Paleontologists collect and classify fossils in an organized fashion• The fossil record has provided convincing evidence for Earth’s evolutionary
past
FEMURPELVIS
Analyze this picture of a baleen whale. Using the idea of evolution by means of natural selection, tell me why this whale has a pelvis and a femur.
PELVIS
FEMUR
Diacodexis(55 m.y.a.)
Pakicetus(52 m.y.a.)
Ambulocetus(50 m.y.a.)
Dorudon(40 m.y.a.)
Baleen Whale(Present day)
• Rhinos are not “ancestors” of pigs
• They share a common ancestor somewhere back in time
• This shows that cows/sheep are closer relatives to pigs than to rhinos or modern whales
Fossil Record• Overall, life which existed more than 500 million years ago was very different
from life today• Although Earth has had extensive oceans for most of its existence, fish fossils
have only been found in rocks 500 million years old or younger• less than 15% of the history of life
Fossil Record• Although most of the top predators today are
mammals such as bear, orcas, big cats, wolves, etc; none of them existed at the time of the dinosaurs or before
• Apart from organisms such as certain types of sharks, cockroaches or ferns, many living organisms today have no identical form in the fossil record
• The modern great white shark has been around from between 11-16 million years!
• Humans (homo sapiens) 50,000-100,000 years ago
• Cockroaches have roamed the planet for as long as 350,000,000 years with little change
Fossil Record• One conclusion that can be drawn from
observing fossils is that life on Earth is CONSTANTLY changing
• Most of the changes have been over huge timescales
• Hundreds of thousands – millions of years
• The fossil record is FAR from complete
Homologous Anatomical Structures• Homologous anatomical structures: which are structures that are similar in
form and function but which are found in seemingly dissimilar species
Homologous Anatomical Structures• One of the most striking examples:
• Five-fingered limb found in animals such as humans, whales, and bats• Called pentadactyl limbs
• Penta= five• Dactyl= fingers
Homologous Anatomical Structures• When we compare a whale’s front fin to the forearm of a human or to a bat’s
wing we find the following bones• Humerus• Radius• Ulna • Carpals
Homologous Anatomical Structures• Although the shape and number of bones may vary, the general format is the
same, DEPITE THE FACT THAT THE FUNCTIONS OF THE LIMBS MAY BE VERY DIFFERENT
What are the different functions of the limbs from different animals?
Homologous Anatomical Structures• Darwin explained that homologous structures were not just a coincidence
but they are evidence that the organisms in question have a COMMON ANCESTOR
Homologous Anatomical Structures• They are of differing sizes and in morphology• BUT, the basic shape and position of the limb bones are the same• THIS WOULD SUGGEST THAT ALL FIVE-FINGERED ORGANISMS HAVE A
COMMON ANCESTOR
EmbryologyEmbryology: The study of embryos• The similar features of embryos in very different organisms suggests
evolution from a distant common ancestor
e
Anatomy of an embryo
Larva
Adult barnacleAdult crab
– identical larvae, but different adult body forms– similar embryos, but look and behave very differently
Darwin studied the embryos of crabs and barnacles:Embryology