The History of Life on Earth

1) What is the current theory of how life arose?

1. small molecules were synthesized
2. these small molecules joined into macromolecules, such as proteins and nucleic acids
3. all these molecules were packaged into protobionts, membrane containing droplets, whose internal chemistry differed from that of the external environment
4. self-replicating molecules emerged that made inheritance possible

2) When was Earth formed (about)?

Earth was formed about 4.6 billion years ago, and life on Earth emerged 3.8 to 3.9 billion years ago.

3) What are stromatolites?

Layered rocks that form when certain prokaryotes bind think films of sediment together.

Facts:

- Amino acids polymerize when added to hot sand, clay or rock.

- The fossil record is largely based on fossils found in sedimentary rocks.

- The absolute ages of fossils can be estimated by radiometric dating and other methods.

- Continental plates move gradually over time, altering the physical geography and climate on Earth.

- Evolutionary trends result from interactions between organisms and their current environments.

Summary:

Earth formed about 4.6 billion years ago, along with the rest of the solar system. Earth’s early atmosphere likely contained water vapor and chemicals released by volcanic eruptions (nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, hydrogen sulfide).Protobionts exhibit simple reproduction and metabolism and maintain an internal chemical environment. Thegeologic record is divided into the Archaean, theProterozoic, and the Phanerozoic eons. The oldest known fossils of multicellular eukaryotes are of small algae that lived about 1.2 billion years ago. first plants were terrestrial, so oxygen atmosphere must develop to produce protective ozone layer. Continental Drift.

At three points in time, the land masses of Earth have formed a supercontinent: 1.1 billion, 600 million, and 250 million years ago. Mammals underwent an adaptive radiation after the extinction of terrestrial dinosaurs. The Hawaiian Islands are one of the world’s great showcases of adaptive radiation.

Extra:

mass extinctions video

The Origin of Species

1) What is microevolution?

Microevolution is the change in the genetic makeup of a population from generation to generation. (adaptations that are confined to a single gene pool).

2) What is macroevolution?

Macroevolution is an evolutionary change above the species level (ex. feathers).

3) What are some factors (from this chapter) that can result with two distinct species formed?

isolation, selection, mutation, genetic drift

Facts:

- The biological species concept emphasizes reproductive isplation

- The two main types of speciation are allopatric speciation and sympatric speciation

- Polyploid speciation occurs in animals but is not common

- Adaptive radiation occurs when many new species arise from a single common ancestor

- Speciation (process by which new species arise) can occur rapidly or slowly, and it can result from changes in few or many genes

diversity!

Summary:

Speciation, the origin of new species, is at the focal point of evolutionary theory because the appearance of new species is the source of biological diversity. Speciation addresses the question of how new species originate and develop through the subdivision and subsequent divergence of gene pools. Species are based on interfertility, not physical similarity. Because the distinction between biological species depends on reproductive incompatibility, the concept hinges on reproductive isolation, the existence of biological barriers that prevent members of two species from producing viable, fertile hybrids.

Reduced hybrid viability. Genetic incompatibility between the two species may abort the development of the hybrid at some embryonic stage or produce frail offspring.Evolutionary biologists have proposed several alternative concepts of species. Two general modes of speciation are distinguished by the way gene flow among populations is initially interrupted. How significant a barrier must be to limit gene exchange depends on the ability of organisms to move about. Individuals of two closely related sympatric cichlid species will not mate under normal light because females have specific color preferences and males differ in color.

Extra:

speciation

The Evolution of Populations

1) What is population genetics?

It is an area of Biology that is keeping track of changes in populations over time > study of genetic variation in populations.

2) What are the conditions under which allelic frequencies (p & q) remain constant from one generation to the next? (Hardy-Weinberg)

- no mutations

- random mating

- no natural selection

- large populations

- no gene flow (immigrations/emigrations; transfer of pollen etc.)

3) What are mutations? Briefly explain both point and chromosomal mutations!

Mutations are the only source of new genes and new alleles.

Point mutations - changes in the base in a gene (impact on phenotype)

Chromosomal mutations - delete, disrupt, duplicate many loci at once (almost certain to be harmful)

Facts:

- Chromosomal mutations delete, disrupt, duplicate or rearrange many loci at once.

- Crossing over occurs during prophase I (meiosis).

- The greater the number of fixed alleles, the lower the species' diversity.

- Modern synthesis looks at the genetic basis of variation and natural selection.

- Natural selection acts more directly on the phenotype and indirectly on the genotype.

Summary:

Hardy-Weinberg stated that under certain conditions (listed in q 2), the gene frequency of a population does not change from generation to generation. The population model described that gene frequencies will not change from one generation to the next even if there are more recessive alleles.

Alteration of genetic frequencies can happen because of natural selection, genetic drift, and gene flow.

natural selection is the only mechanism that constantly causes adaptive evolution.

Extra:

Hardy Weinberg principle example video

Descent with Modification: A Darwinian View of Life

1) Explain some of the Pre-Darwinian Views of Life!

Greek Philosophers: Plato (organism perfectly adapted to the environment), Aristotle(Scala Naturale - a scale of increasing complexity

Fixed Spicies Concept: the Creator had designed each and every species for a particular purpose

Catastrophism: fossils related to current life (Georges Cuvier); fossils were remains of species lost due to a catastrophe

Gradualism - Hutton: profound change is the product of slow, but continuous processes

Uniformatarianism - Lyle: geological processes à operated at the same rate over the Earth’s history à the Earth must be very old!

Lamarck's Theory: life changed to complex from simple over time
a) use/disuse - body parts used to survive become larger and
stronger; body parts not used to survive deteriorate
b) acquired characteristics - modifications acquired by use/disuse
are passed on to offspring

2) What are endemic species?

Species found at certain geographical locations and nowhere else.

3) What are some signs for evolution?

biogeography, fossils, taxonomy, comparative anatomy, comparative embryology,molecular biology...

Facts:

- Lamarck recognized that species evolve, though his explanatory mechanism was flawed.

- Fossils provide evidence for the theory of evolution.

- Evolution is change in species over time.

- Heritable variations exist within a population.

- These variations can result in changes in the genetic composition.

Summary:

Evolution includes changes over time, and is continuous (still occurs).

Ideas about change over time include fossils, paleontolgy, catastrophism, uniformitrarianism. Lamarck first provided with his hypothesis. Later, Charles Darwin defined the natural selection and supported his ideas.

Many evolutions that have to do with ancestors and environments have been contemplated and discovered.

Extra:

Evolution (of dance) video

Genomes and their Evolution

1) What is genomics?

The study of the whole set of genes and their interactions.

2) What is a homebox?

Homebox is a 180-nucleotide sequence that specifies a 60-amino-acid homeodomain in the encoded proteins.

3) Explain the whole-genome shotgun approach to genome sequencing!

The whole genome is cut into many small, overlapping fragments that are sequenced; computer software then assembles the complete sequence. Correct assembly is made easier when mapping information is also available.

Facts:

- Websites on the Internet provide centralized access to genome sequence databases, analytical tools and genomerelated information

- Only 1.5% of the human genome codes for proteins or gives rise to rRNA or tRNA; the rest is noncoding DNA, including repetitive DNA

- Genomes vary in size, number of genes, and gene density

- Biologists in the field of evo-devo compare developmental processes of different multicellular organisms

- Duplication, rearrangement, and mutation of DNA contribute to genome evolution

Summary:

Sequencing the human genome is the most ambitious mapping project. It officially began as the Human Genome Project in 1990, in major, going through three stages: genetic mapping, physical mapping, and DNA sequencing. Humans have 20,488 genes and we can make 75,000 polypeptides. Humans and other mammals have the lowest gene density and the number of genes is not correlated to genome size.

It seems that the rate of duplications and inversions have accelerated about 100 million years ago.

Extra:

DNA Genechip

DNA Technology and Genetics

1) What is biotechnology?

The manipulation of organisms or their components to make useful products.

2) List some methods of biotechnology!

1.Bacteria Transformation

2.Restriction Enzymes

3.cDNA

4.DNA Sequencing

5.PCR

6.RFLP

3) What are the steps for plasmid use?

1. Get the DNA for the trait.

2. Insert DNA into the plasmid.

3. Bacterial Transformation.

4. Identification of the new trait.

Facts:

- The practical applications of DNA technology affect our lives in many ways.

- DNA cloning and other techniques, collectively termed DNA technology, can be used to manipulate

and analyze DNA and to produce useful new products and organisms.

- Restrictive enzymes cut DNA at specific nucleotide sequences called “restriction sites”

- Markers are inherited in a Mendelian pattern and can show relationships (Pedigree studies).

- PCR can produce many copies of a specific target segment of DNA, using primers that bracket the

desired sequence and a heat-resistant DNA polymerase.

Summary:

DNA cloning yields multiple copies of a gene or other DNA segment. DNA technology allows us to

study the sequence, expression, and function of a gene. The DNA practical applications of DNA

technology affect our lives in many ways.

Extra:

The PCR song

Viruses

1) What is a capsid?

A capsid is a protein shell that surrounds the genetic material.

2) How are the viruses that infect bacterial cells called?

Bacteriophages (Phages)

3) What does limited host range mean for viruses?

Viruses have a limited host range. This means they can infect only a very limited variety of hosts. Ex. human cold virus infects only cells of the upper respiratory tract.

Facts:

- Researchers discovered viruses in the late 1800s by studying a plant disease, tobacco mosaic disease.

- The genome of a virus can be single or double stranded DNA or RNA

- Phages can reproduce two alternative mechanisms: the lytic cycle and the lysogenic cycle.

- Viruses can reproduce only within cells

- Viroids are naked RNA molecules that infect plants and disrupt their growth.

Summary:

Viruses are particles of nucleic acids, proteins, and, in some cases, lipids. It is in common to all viruses that they enter living cells and, once inside, use the machinery of the infected cell to produce more viruses. Viruses are parasites, not considered to be living things because they are not made up of cells. Once the virus is inside a host cell, two different processes may occur and they are lytic infection and lysogenic infection.

There are viruses that cause diseases and they are called pathogens.

Extra:

HIV virus structure video