Goal 3 - Evolution Patterns Notes
What was early Earth Like?
Very hot. The energy from colliding meteorites heated the surface of the earth; compression of minerals and from the decay of radioactive materials heated the interior of the earth.
Around 4.4 billion years ago earth cooled enough for water in the atmosphere to condense leading to millions of years of rainstorms with lightening – enough for the rain to fill depressions creating Earths oceans.
Very hot. The energy from colliding meteorites heated the surface of the earth; compression of minerals and from the decay of radioactive materials heated the interior of the earth.
- Volcanoes might have frequently spewed lava and gases – relieving some pressure in Earth’s interior. Gases helped form Earths early atmosphere.
- Atmosphere contained no free oxygen, but water vapor, carbon dioxide and nitrogen. Man could not have lived.
Around 4.4 billion years ago earth cooled enough for water in the atmosphere to condense leading to millions of years of rainstorms with lightening – enough for the rain to fill depressions creating Earths oceans.
- Some scientists propose life originated in earths oceans around 3.9-3.4 billion years ago.
Rocks Reveal Earth's History
History in rocks
Oldest rocks that have been found on the earth formed around 3.9 billion years ago.
Fossils
Oldest rocks that have been found on the earth formed around 3.9 billion years ago.
- Rocks give info about diversity of life that has existed on the planet.
Fossils
- Scientist study fossils to learn about ancient species. Fossils are evidence of an organism that lived along time ago.
- Paleontologists study fossils to understand events that happened a long time ago. Fossils can give information about the kinds of organism that lived in the past and about their behavior – how they moved and what they ate. Also give information about ancient climates.
- Fossils form when an organism gets buried in the mud, sand, or clay soon after they die – rapid burial. They particles become compressed over time and harden into sedimentary rocks.
Relative Dating of Rocks and Fossils
Relative Dating Rocks and Fossils
The principle of superposition - in a vertical sequence of sedimentary or volcanic rocks, a higher rock unit is younger than a lower one. "Down" is older, "up" is younger.
The principle of original horizontality - rock layers were originally deposited close to horizontal.
The principle of original lateral extension - A rock unit continues laterally unless there is a structure or change to prevent its extension.
The principle of cross-cutting relationships - a structure that cuts another is younger than the structure that is cut.
The principle of inclusion - a structure that is included in another is older than the including structure.
The principle of "uniformitarianism" - processes operating in the past were constrained by the same "laws of physics" as operate today.
The principle of superposition - in a vertical sequence of sedimentary or volcanic rocks, a higher rock unit is younger than a lower one. "Down" is older, "up" is younger.
The principle of original horizontality - rock layers were originally deposited close to horizontal.
The principle of original lateral extension - A rock unit continues laterally unless there is a structure or change to prevent its extension.
The principle of cross-cutting relationships - a structure that cuts another is younger than the structure that is cut.
The principle of inclusion - a structure that is included in another is older than the including structure.
The principle of "uniformitarianism" - processes operating in the past were constrained by the same "laws of physics" as operate today.
A More Exact Way to Date Rocks and Fossils
Radiometric Dating
Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks.
When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside. Afterwards, they decay at a predictable rate. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed.
Fossils are generally found in sedimentary rock—not igneous rock. Sedimentary rocks can be dated using radioactive carbon, but because carbon decays relatively quickly, this only works for rocks younger than about 50 thousand years.
Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks.
- The universe is full of naturally occurring radioactive elements. Radioactive atoms are inherently unstable; over time, radioactive “parent atoms” decay into stable “daughter atoms.”
When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside. Afterwards, they decay at a predictable rate. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed.
Fossils are generally found in sedimentary rock—not igneous rock. Sedimentary rocks can be dated using radioactive carbon, but because carbon decays relatively quickly, this only works for rocks younger than about 50 thousand years.
- So in order to date most older fossils, scientists look for layers of igneous rock or volcanic ash above and below the fossil. Scientists date igneous rock using elements that are slow to decay, such as uranium and potassium. By dating these surrounding layers, they can figure out the youngest and oldest that the fossil might be; this is known as “bracketing” the age of the sedimentary layer in which the fossils occur.
Evidence of Evolution - Fossils
Fossils
- Provide a record of early life and evolutionary history.
- Not complete, missing evidence of changes.
- Found throughout the world.
- Fossils in the lower strata are typically older than those in the overlying strata.
- Fossils in the upper strata are generally more complex than those in the lower strata, which may contain simpler life forms.
- Fossils in the upper strata are different from those in the lower strata, but there is often a resemblance between them. This suggests a link between the modern and older forms – COMMON ANCESTOR.
- Some fossils in the lower strata are unlike any modern living things. This suggests that some organisms have died out, or become extinct.
- Some fossils however are very similar to modern life forms, suggesting some have undergone little evolutionary change.
Evidence of Evolution - Anatomy
Homologous Structures
- Traits that are similar in different species (similar shape but different function). Suggests a common ancestor.
- Examples: the human arm, the wing of a bird, and the flipper of a whale.
Evidence of Evolution - Anatomy
Vestigial Structures
- Structures that are inherited but no longer used or have greatly decreased importance– similar to a structure that is used in other species. A body stricture in a present day organism that no longer serves it original purpose but was useful to an ancient ancestor. A structure becomes vestigial when the species no longer needs the feature for its original function, yet it is still inherited as part of the body plan for the species.
- Examples – whale pelvic girdle (necessary for walking), eyes in blind mole rat and cave fish, snakes have remnants of legs.
Evidence of Evolution - Embrology
Embryology
Embryo – earliest stage of growth and development of both plants and animals. All embryos of different species (fish, birds, mammals) look similar. They have tails and pharyngeal pouches. In fish the pouches develop into gills. In mammal and reptiles and birds they develop into parts of the ears, jaws, and throat. It is the shared features in the young embryos that suggest that evolution came from a distant common ancestor
Embryo – earliest stage of growth and development of both plants and animals. All embryos of different species (fish, birds, mammals) look similar. They have tails and pharyngeal pouches. In fish the pouches develop into gills. In mammal and reptiles and birds they develop into parts of the ears, jaws, and throat. It is the shared features in the young embryos that suggest that evolution came from a distant common ancestor
Evidence of Evolution - Biochemistry
Biochemistry
DNA and cytochrome C which is an enzyme. (Remember an enzyme is a special protein (made up of amino acids) that speeds up chemical reactions). Organisms that are biologically similar have fewer differences in their amino acid sequences. Groups that share more similarities are interpreted as being more closely related or as sharing a common ancestor. Today biologists also use DNA and RNA nucleotide sequences to construct evolutionary relationships. The closer the relationship between organisms, the greater their biochemical similarities.
DNA and cytochrome C which is an enzyme. (Remember an enzyme is a special protein (made up of amino acids) that speeds up chemical reactions). Organisms that are biologically similar have fewer differences in their amino acid sequences. Groups that share more similarities are interpreted as being more closely related or as sharing a common ancestor. Today biologists also use DNA and RNA nucleotide sequences to construct evolutionary relationships. The closer the relationship between organisms, the greater their biochemical similarities.
Evidence of Evolution - Adaptations
Adaptation is any variation that aids in an organisms chance for survival in its environment.
Structural Adaptations - Develop over many generations. Help organisms survive in their environments (examples porcupines quills – defense, mole rats large teeth and claws – defense and digging).
Structural Adaptations - Develop over many generations. Help organisms survive in their environments (examples porcupines quills – defense, mole rats large teeth and claws – defense and digging).
Evidence of Evolution - Adaptations
Physiological Adaptations – Occur quickly. Physiological adaptations are changes in organism’s metabolic processes. Examples bacteria develop physiological adaptations to prevent being killed by penicillin, insects and weeds have become resistant to chemicals used to kill them.
Evidence for Evolution - Adaptations
Mimicry – enables one species to look or to resemble another species. A harmless species can physically resemble a more harmful one so predators will avoid it (example fly that looks like as wasp)
Evolution of Evolution - Adaptations
Camouflage – allows a species to blend with surroundings. Camouflaged organisms not easily found by predators, thus can survive to reproduce.