Biology 1001A Lecture 18: Biology Lecture 18.docx

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ochrebee715

30 Apr 2012

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When we say how closely related or how distantly related are two species, what we really mean is how far back in evolutionary time did they last share a common ancestor. Patterns in macroevolution: most of what we know of macroevolution comes from the fossil record. In order to form and preserve fossils, many conditions have to be met: the vast majority of species that have lived have never completely formed fossils, not everything is equally likely to fossilize (biased) Temporal biases: you are more likely to find a new fossil then an ancient fossil. Taxonomic biases: some organisms are more likely to fossilize than others because of the body parts or structures they have (example: animals with hard shells, teeth, bones are able to fossilize well) Habitat biases: some habitats just have better conditions for fossil formation (example: marine conditions are great for fossil formations) Evolutionary trends: cope"s rule: body size tends to increase over evolutionary time.

Related Questions

Fossils discovered tell stories of how past organisms were very different from those presently living. The sweeping changes in life on Earth as revealed by fossils revealed by fossils illustrate macroevolution, the broad pattern of evolution above the species level. Describe how gene flow, genetic drift, and natural selection all can influence macroevolution.

ivorydolphin134

You are standing at the bottom of a deep canyon in East Africa. While looking at the canyon walls, you notice that there are fairly distinctive layers of soil and rock. In a layer at about your knee level you see a skull (#1) with big teeth and a small cranium (and therefore a small brain). You look upward and in a different layer that is at about eye level you see another skull (#2). It is very similar to the first, but you notice some differences. The teeth are smaller but the cranium is larger. Given this information, answer the following three questions.

1. Which skull is older, #1 or #2?

2. Is that assessment based on relative dating or chronometric dating? Which specific technique is utilized?

3. If you infer that the two skulls are so similar that they are related, but different enough to be different species, does this represent microevolution or macroevolution?

limeyak247

We have discussed in class that fossils show evidence for evolution. This is shown with stunning clarity when the fossil record is complete as with the horse. However, there are instances where the fossil record is not complete which means there are gaps. Someone comes to you and states that because there are gaps in the record for species "A" this shows that evolution is not true. How do you argue against this statement? In other words how do you argue in favor of evolution when gaps are present? Or do these gaps invalidate evolution? Restrict your discussion to the fossil record only.

Biology 1001A Lecture 18: Biology Lecture 18.docx

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