Evolution Lecture 7

Question 1

Fossils

Answer 1

Preserved remnants (or traces) of past life in rock. Some examples are:
– Mineral components
– Petrified organic material
– Casts
– Trace fossils (footprints etc)
It tells us information about past ecosystems; climate;
sea levels etc., & dating of geological record. More direct view of evolutionary history than from living organisms. They are biased for species the existed for a long time.

Question 2

Sedimentary Rock

Answer 2

Where most fossils are found. They are found in the bottom of lakes, layers keep adding show a passage of time. Where mineral particles fall into the water bodies then form layers (other dead animals can get trapped here then are in the rock before they fully decay). They then get compared by heat into solid rock over many years.

Question 3

Why is the sedimentary rock slanted?

Answer 3

Because it’s very very old.

Question 4

Where can fossils also be found?

Answer 4

Frozen in ice or in amber (tree sap).

Question 5

Strata

Answer 5

Sedimentary rock layers.

Question 6

Archaeopteryx

Answer 6

Fossil of a dinosaur with feathers seen in it. It’s an articulated fossil because it’s all intact.

Question 7

Index Fossil

Answer 7

Common, widespread fossils characteristic of particular periods of earth’s history. Crucial for ‘relative dating’ in geological record. Eg. shells of single cell organisms.

Question 8

What can we find out about extinct things from extinct?

Answer 8

Their biology and age.

Question 9

The geological record

Answer 9

The fossil record is in this. There is a relationship between them. Earth is ~4.6 billion years old. (Microbial) life arose ~3.5+ billion years ago. Fossils of animals & plants common in the last ~550 million years: “Phanerozoic Eon.”

Question 10

Phanerozoic divided into three what?

Answer 10

Eras

Question 11

Each Era subdivided into several what?

Answer 11

Periods

Question 12

The three Eras in order?

Answer 12

Paleozoic, Mesozoic, Cenozotic. This is the last 15% of earths time.

Question 13

When were the eras worked out?

Answer 13

In the 19th century using many different dating methods, such as index fossils. 20th century use radioactive decay allowed to be sure if date rocks.

Question 14

Radioactive Decay

Answer 14

Radioactive parent isotope decay to a daughter isotope at a charcuterie rate.

Question 15

Half-life

Answer 15

the time required for 50% of the parent isotope to decay.

Question 16

Periods

Answer 16

Subdivisions of eras. They aren’t the same length.

Question 17

How did the period change occur?

Answer 17

Saw a sudden change in the geological record, where the fossils in rocks changed into different rocks. (the eras change is the same but with bigger differences).

Question 18

Mass extinctions

Answer 18

Many species extinct in very short time. Causes: large environmental changes. Plausible examples:
– Massive volcanic activity
– Impact by asteroid or comet
Major importance in history of life. Extinction occur all of the time. Only the survivors can speciate.

Question 19

How many mass extinction are there?

Answer 19

5 big ones, most marking ends of Eras/Periods.

Question 20

End-Permian mass extinction

Answer 20

~250 million years ago. Most devastating mass extinction. Extinction of ~90% of species on earth. Many large taxa went totally extinct (e.g. ~50% of Families). Guessed that it was caused by volcanoes.

Question 21

End-Cretaceous mass extinction

Answer 21

~65 million years ago. Most recent ‘big’ mass-extinction. Extinction of ~50% of species on earth
e.g. dinosaurs (other than birds). Several marine invertebrate groups. An astroid hit, the dust from it would block the. sun, this would stop photosynthesis, and food chains.

Question 22

Adaptive radiations

Answer 22

Rapid speciation and evolutionary change in underexploited habitats. They have a small # of competitors. Many species come to be in a short period of time. They start to differ from each other very quickly.

Question 23

Two types of Adaptive radiations

Answer 23

Regional: Eg. colonisation of new island chains

World-wide: It can recover diversity after a while.
– Following mass extinction events.
– Only surviving lineages can radiate!
– Replacement in fossil record

Question 24

Hawaiian ‘Silversword alliance’ example?

Answer 24

Plant group, endemic to Hawaii (very isolated, ‘young’ island group formed by volcanic activity). ~50 species; great variation in size, shape. All descended from one species, in last ~5 million years. the species are genetically similar to each other.

Question 25

Adaptive radiation of mammals after End-Cretaceous
extinction?

Answer 25

When there was dinosaurs, all mammals were small-medium sized. After the dinosaurs went extinct mammal became the large land animals.

Question 26

Complex Adaptations

Answer 26

Adaptations that have many parts to it. All parts are need to preform the function well.

Question 27

How do complex adaptations evolve?

Answer 27

When ‘Darwinian’ evolution proposes:
– evolution through many small steps. They weren’t very different from what was there. (graduison)
– every ‘step’ should improve fitness
However, natural selection doesn’t have foresight and can’t predict that it will happen in the future.

Question 28

Camera Eye Example?

Answer 28

A giant squid eye. The lens move forwards and back, while the humans change the shape of the lens. Both have the same function. The eye has many parts to it to make it work.

Question 29

Some mechanisms for evolution of complex adaptations?

Answer 29

1) Intermediates that are actually capable of
functioning

2) Modification of existing structures with
different functions

3) Larger ‘steps’ (than imagined by Darwin).
* e.g. Changes in developmental regulation
* Origin of novel genes, e.g. Gene duplication

Question 30

Functioning Intermediates

Answer 30

In many cases, simpler forms of complex structures are functional.
– Evidence: Organs of different
complexity in related species
– Step-wise evolution plausible
Functional eyes of different complexity in different living Molluscs. They are well suited to their biology and environments.

Question 31

Modification of existing structures

Answer 31

Exaptation: Structures adapted for one function are
coincidently useful for another function. Starting from something that’s already complex. How some dinosaurs had simpler wings for insulation, and how some birds have contour feathers that are quite complicated for flight.

Question 32

The evolution of developmental regulation?

Answer 32

Mutations affecting genes that control development. Small genetic change can result in large, coordinated changes in phenotype.

Question 33

Development biology

Answer 33

How complex organisms develop overt their lifetimes from very simple organisms (zygote). Genes that control early stages in development can end up small changes in their expression patents or in their animo acid sequences.

Question 34

Heterochrony

Answer 34

An evolutionary change in the rate of timing of developmental events.

Question 35

Orthologous genes

Answer 35

The homology is the result of a speciation event and hence occurs between genes found in different species.

Question 36

Homeotic genes

Answer 36

Master regulatory genes

Question 37

Hox genes

Answer 37

Control identity of segments along developing animal body.

Question 38

Fruit fly example?

Answer 38

The wild type fruitfully and homeotic mutant only are different by just a couple of nucleotide difference (in the Hox genes). The mutant grows up to be an adult but wouldn’t do well in nature.

Question 39

Difference between a nucleotide sequence and changes in regulation of gene expression?

Answer 39

A change in nucleotide sequence may affect its function whenever the gene is expressed, while changes in the regulation of gene expression can be limited to one cell type. Thus a change in the regulator of a developmental gene may have fewer harmful side effects than a change to the sequence of the gene.

Question 40

Hemoglobin Example?

Answer 40

hemoglobin and myoglobin both carry oxygen. When your muscle needs oxygen it takes it from the myoglobin, which takes it from the hemoglobin. The hemoglobin circulates in blood to get recharged with oxygen. Hemoglobin have 4 polypeptides together, and two subtypes alpha and beta which are different proteins. It is because gene duplication resulted in hemoglobin and myoglobin, then it happened again to get the alpha and beta.

Question 41

Gene Duplication

Answer 41

How new genes evolve. During DNA synthesis that process mitosis copying of one segment of DNA twice, it can also happen in meiosis called unequal crossing over. Once this happens the genes are at two separate loci, and are independent of one another. Over time they can have evolutionary changes and acquire new differences. These are paralogs.

Question 42

Paralogs

Answer 42

The two related genes in one genome.

Question 43

Another way to get new genes?

Answer 43

Lateral/Horizontal Gene Transfer