CHAPTER 11

IDEAS ABOUT THE ORIGINS OF LIFE

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Door Number One,…

Extraterrestrial Origin – origin outside ofEarth. Life was carried here by asteroid ormeteorite.

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Door Number Two,…

Divine Creation – the process that gave rise to life was driven by forces that cannot be explained by science. Gen. 1:1 In the beginning God,…

NOTE: a belief is not the same as a scientific hypo. Any hypothesis is subject to a test which may prove it false. Divine creation is a belief and not a hypo. It falls outside the realm of science.

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Spontaneous Origin – Earth developed itself through natural chemical and physical processes. Molecules of nonliving matter reacted chemically and formed simple organic molecules. These molecules copied themselves and became more complex. This can be copied by scientific methods, but cannot account for the source of the molecules. All organisms are composed of the same basic chemicals,…

,…Proteins, lipids, carbohydrates, and nucleic acids,…and these are composed of the elements C, H, O, and N.

CHAPTER 12 THE THEORY OF

EVOLUTION

(The Work of Charles Darwin)

Theory of Evolution – four main parts.

1)Variation exists within the genes of every species. This is caused by random mutation.

2)In a particular environment, some individuals are better suited for survival and so leave more offspring. This is called natural selection.

3)Species change over time. If they do not change or adapt to their environment, they will become extinct.

4)The fossil record supports the statement that species change over time.

One early explanation of evolution,...Lamarck made one of the first attempts to explain evolution with his theory of acquired characteristics, which stated that a structure developed or dis- appeared because of its “use or disuse”. E.g. a giraffe stretched its neck getting leaves and passed this trait to its offspring.

Darwin’s Research aboard the HMS Beagle-He departed England in 1831 as the ship’s naturalist on a 5-year voyage to study plants and animals off the coast of South America.-He left as a creationist, believing that each species was a divine creation, unchanging and existing as it was originally created. Creationism didn’t explain the kinds and distribution of fossils.

-He made many observations visiting the Galapagos Islands off the coast of South America (now Ecuador). He noticed that animals there resembled those from the coastal areas of South America. For example, the Galapagos finches with beaks specialized for the type of food they ate. Though each different, they closely resembled those on the coast of S.A.

                                                               

Darwin Sought an Explanation for Evolution

Malthus in 1798 –proposed,…-The human population increased in a geometric progression (multiply) while the food supply increased in an arithmetic progression (addition).-However, this doesn’t really occur because of disease, war, and famine (human environment).

Population –Individuals of the same species that live in a defined area and breed with each other.-a population could go way beyond the food supply,…-this normally doesn’t happen because of predators, weather, and availability of water and shelter (environment)

Natural Selection – process by which populations change in response to their environment.-Individuals that possess superior physical or behavioral attributes are more likely to survive than those not so well adapted.-They are also more likely to breed and pass on their traits.

Arctic hare

Adaptation – changing of a species that results in being better suited for the environment. Those best suited will survive.

Origin of Species – book written by Darwin that has had a strong and lasting impact.-Presented a body of evidence that evolution has occurred.-Presented a hypothesis explaining how evolution takes place.

Darwin’s Ideas UpdatedNatural selection causes the frequency of certain genes to vary over time (death of those not fit to breed or those not breeding).-Mutations and recombination of genes (via sexual reproduction) are sources of new variation.-This results in microevolution – changes that occur among species over time (ex- the selective breeding of crops-Fig 12-7)

Isolation leads to species formation. -Two populations of the same species become separate/isolated from each other (by a river, canyon, ocean, etc.) -The members of each population may become different, and are then considered to be different species.

Me,…extinct,…NEVER!!!

Extinction leads to species replacement. -Climate changes or natural disasters (flood, fires, mud slides, volcanoes, meteorites) cause extinctions.

-Species that have become extinct will be replaced by another species using their area.-Results in macroevolution – change that occurs among species over time as new species evolve and old species become extinct (mammals replacing dinosaurs)

What evidencedo scientists use to prove macro-evolution?

Fossils – preserved or mineralized remains (bone, tooth, or shell) or traces (footprint, burrow, or imprint) of an organism that lived long ago

Fossils – preserved or mineralized remains (bone, tooth, or shell) or traces (footprint, burrow, or imprint) of an organism that lived long ago

Evidence of Macroevolution

Vestigial structures -Body part reduced in size or no longer functional Example: whale’s vestigial pelvis

ANATOMY & DEVELOPMENT

Embryology

--Embryo = early stages of organism’s development

--Animals have very similar embryos

Chicken

Human

DNA-All living things are made of DNA-DNA shows that some animals are more closely “related” than others-Example: dogs are more closely related to bears than to fish so the DNA of dogs is more like bear DNA than fish DNA

Homologous structures -Many structures of organisms are similar-Example: bones in the human hand, bat’s wing, whale’s flipper

Whale’s flipper

Bat’s wing

•Gradualism--rate of evolution is steady (example: horses)

According to scientists, horses were first small, had 4 toes, and sharp teeth (meat-eater)

Eohippus— “dawn horse”

•Punctuated equilibrium--evolution can be rapid and in spurts (example: elephants)

Darwin wrote: “Can we doubt…that individuals having any advantage, however slight, over others, would have the best chance of surviving and procreating their kind? … This preservation of favorable variations, I call Natural Selection.”------ Natural Selection leads to microevolution, which is the change within a species that occurs over time.

EVIDENCE OF MICROEVOLUTION

Industrial Melanism in Industrial Melanism in Biston betulariaBiston betularia (peppered moth)-Light & dark variety of moths present-Light was predominant before Industrial Revolution-Trees darkened w/pollution which allowed for the dark variety to become predominant (Read p. 261)

Sickle Cell Anemia (Reveals Evidence of Microevolution)

If individuals homozygous for sickle cellanemia die early, then why hasn’t the allele for that trait entirely disappeared?

Balancing Selection,…in central Africa, natural selection affects sickle cell anemia in opposing ways,…(1)it tends to eliminate the sickle cell allele because it is lethal to homozygous individuals, and (2)it tends to preserve the allele because heterozygous individuals are resistant to malaria.

The sickle cell allele has no benefits for individuals in the U.S. because we no longer are faced with malaria. Therefore the number of people with that allele is decreasing. When natural selection is unopposed, the frequency of a particular allele tends to move in one direction—in this case, toward elimination. Biologists call such unopposed selection directional selection.

Divergence – the accumulation of differences between groups (populations, species, genera, etc.)

According to scientists,…Divergence then leads to the formation of new species, a process known as speciation.

Ecological races – populations of the same species that differ genetically because of adaptations to different living conditions Reproductive isolation – the prevention of mating between formerly interbreeding groups or the inability of these groups to produce fertile offspring