Evolution 3
Do living organisms help prove the theory of evolution?
You might remember that classification is done by studying similarities and differences between different organisms. The remarkable similarities between some species has led scientists to conclude that similar species have evolved from a common ancestor. In many cases, the fossil remains of these common ancestors have been found. Comparing these remains with living organisms has added to the evidence for organic evolution
Comparative Anatomy - the study of structural similarities and differences between living things. Similarities provide evidence for evolutionary relationships
The structures pictured above are quite different in appearance because they are adapted to perform different functions. Even with these different functions, internally the structures of these organs are surprisingly similar. They all have the same number of bones arranged in a similar way.

Homologous Structures - parts of different organisms that have similar structures and development, but have different forms and functions.same structure – different function
Analagous Structures - structures that have similar external forms and functions but are different internal structures. IE.
Bird wings and insect wings same function – different structure
Vestigial Structures - remnants of structures that were functional in an ancestral form. They are smaller in size and serve little or no function. IE coccyx (tailbone), appendix, etc.
Embryological similarities:
??What is an embryo??
The presence of similarities between embryos of different species shows evidence for evolution. The more closely related the animals, the longer they continue to resemble one another as they develop.

Molecular evidence…
Because all DNA is descended from the DNA carried by the earliest life forms, the DNA of all organism shares a common genetic code. The more closely related organisms are, the more
DNA (molecular similarities) they share.
Evolution 4
What is the modern theory for the beginning of life?
Today, most scientists believe in Biogenesis. Biogenesis is the theory that life can only come from another form of life.
Spontaneous Generation – life from non-life

-But where did the first form of life come from??-
The Heterotroph Hypothesis is a theory proposed by many scientists to explain how life originated on earth.
The Environment:
The environment on earth was much different in the beginning…
The Beginning
Hydrogen, Water Vapor,
Ammonia, and Methane
Very Hot
Now
Nitrogen, Oxygen, and
Carbon Dioxide
Much Cooler
Energy:
The synthesis of organic compounds from inorganic raw materials requires energy.
Sources of energy on earth:
-Heat
-Radioactive decay
-Lightning
-Ultraviolet light, visible light, and X-rays
These energy sources could have made nucleotides + amino acids.

The Miller Experiment:
Aggregates:
The heterotroph hypothesis also states that protein-like substances that could be formed under these conditions may have formed ___________, or clusters, of large molecules. He called these ____________. The
coacervates are covered by a layer of water that help chemical reactions happen faster. Coacervates would absorb nutrients from the environment and eventually split. These were primitive living things.
Respiration and Photosynthesis:
Due to the fact that primitive earth did not contain oxygen, it is believed that living things on earth created energy using Anaerobic Respiration

Eventually, organisms would develop that could use light as a source of energy. These photosynthetic autotrophs would be the first to add oxygen to the atmosphere.
The addition of oxygen to the atmosphere would lead to organisms that could carry out Aerobic Respiration. At the same time, added ozone would begin to block the Xrays and ultraviolet rays produced by the sun. The earth would be changed forever.
Name
:________
Evolution Week 1 Questions
What is a fossil?
Name six types of fossils.
In what kind of rock are most fossils found?
What is the fossil record?
Where is it not possible to use correlation?
What are index fossils?

List two patterns of evolution that can be seen in the fossil record.
Other than the fossil record, what other evidence supports the theory for organic evolution?
Define homologous structures and analogous structures?
What is spontaneous generation?
How was spontaneous generation disproved?
What is biogenesis?
What is the name of the theory that explains the origins of life?
Critical Thinking:
Why would the fossil of an organism that lived only in one location be a poor index fossil?