Evolution
Chapter 28

How did humans, as well as as other species that are alive today come to their existence?

 

I. Evolution- is a change through time which is based on theoretical concepts & assumptions

 

A. Evidence that supports the theory of evolution comes from many different sources: including fossils from the

1) geological record

 As well as studies that show comparisons among different kinds of organisms in the areas of

2) cytology (cell study) 

3) biochemistry

4) embryology 

5) anatomy

1) Geological record- geologists estimate that the earth is 4.6 billion years old

In strata (undistributed layers) of sedimentary rock, it is possible to find fossils in upper strata that resemble those in lower strata, even though they are clearly of different species. This fact leads support to the theory that genetic links between modern life forms & ancient life exist.

It also suggests that genetic links exists among diverse modern life forms by virtue of their common links to ancestral species.

[For example, it is thought that all vertebrate species, from fish to mammals, share a common chordate ancestor that lived millions of years ago.] It is thought that modern species having similar structures share these ancestral forms.

This concept of common ancestry, in which 2 divergent forms can trace their inheritance to a single preexisting life forms, is eccential to an understanding of the science of evolution.

What is a fossil? great web site, "must see"
fossils- are any trace of or remain of an organism preserved by natural processes
-types of fossils include: amber, ice, bones, petrifaction, molds, casts, & imprints

 

2) Comparitive Cytology-

a. all living things are made of cells
b. list some differences between plant & animal cells

 

3) Comparative Biochemistry-

a. DNA & protein structure is similar in closely related species
examples: insulin & thyroxine from a pig, cow & sheep can be used to treat humans

 

4) Comparative Embryology-

a. reproductive process is similar in different organisms
b. the existence of the amnion in the egg of a bird & the uterus of a mammal
c. also embryos of most vertebrates show a great deal of similarity in early stages of development
d. analogous structures- structures found in different types of organisms that are similar in function or outward appearance, but dissimilar in basic structure or embryological development
e. EXPLORATORIUM- this web site is an virtual activity that will allow you to identify different embryos

 

5) Comparative Anatomy

a. similar organisms can be shown to have limbs, internal organs, or other structures that are constructed similarly
b. homologous structures are believed to have originated from common ancestral forms of the same organ (THIS DOES NOT NECESSARILY MEAN THAT THEY FUNCTION IN THE SAME WAY)

As we learned in the beginning of the year, the Cell Theory states that all cells arise from previously existing cells. Can you explain where the first cell came from?

 

II. Heterotroph Hypothesis- ORIGIN of LIFE

 

A. 4.6 billion years ago the earth was comprised of water (H2O), ammonia (NH3), methane (CH4), hydrogen (H2)

B. there was also sun's X-rays, & ultraviolet radiation which was unfiltered, lightening and volcanic activity

C. the hypothesis believes these components synthesized simple biochemical molecules (example: simple sugars, amino acids, & lipids)

D. these substances formed longer "chain" molecules of polypeptides, polysaccharides, & hydrocarbons

1. These same "molecular chains" are represented in the FLUID MOSAIC MODEL which is a model of the structure of the cell membrane in which large protein molecules are thought to be embedded in a bilipid layer.

E. Stanely Miller set up an experiment that supports the idea of the heterotroph hypothesis.