BIOS 1107 Test 1

1.1-1.6

Six criteria for life

1. Need for energy

2. Organization in membrane-bound cells

3. Genetic information

4. Ability to replicate

5. Change over time

6. Growth and response to stimuli

Evolution

Change in the heritable characteristics of a population

3 domains of life

Bacteria, Archaea, Eucarya

The feature common to all three domains of life

The genetic material of DNA

A feature common to only Bacteria and Archaea

Prokaryotes (no nuclei)

Biological Evolution

The change in allele frequency of a population

Evidence of evolution

1. Geological and fossil records

2. Homologies in body plans, structures, and DNA sequences

3. Common Biochemistry of all life (same set of amino acids, molecular building blocks, and universal genetic code)

4. Genetic data matches fossil records, supporting a common origin for all living organisms

Homologous structure

Similarity is due to inheritance from a common ancestor

Analogous structure

Species evolving independently, even if they have similar features

Fitness

The ability of an organism to produce viable progeny relative to others in the population

Viable projeny

Offspring that can survive and reproduce

Adaptation

Heritable trait that increases survival and reproduction for the offspring (of the mechanisms of evolution, only natural selection results in adaptation)

Evolution by natural selection

Survival of certain phenotypes in a population as well as a result of environmental pressures

Evidence for evolution by natural selection

1. The trait must be variable in the population so one encoding gene has more than one variant/allele

2. The trait must be heritable, encoded by a gene(s)

3. The struggle of existence, where many more offspring are born than can survive

4. Individuals with different alleles have differential survival and reproduction governed by the fit of the organism to the environment

Stabilizing selection

Directional selection

Disruptive selection

Balancing selection

5 mechanisms of evolution

1. Mutation

2. Gene Flow

3. Genetic Drift

4. Non-Random Mating

5. Natural Selection

Mutation

Variation in the new genome. This can produce new alleles affecting the frequencies present. It is random and has low occurance.

Caused by:

• Errors/mistakes in DNA replication

• Exposure to mutagens (chemicals, radiation) that damage the DNA

Genetic Drift

The random change in allele frequency over time.

Founder effect

A type of genetic drift -

When a subset of a population gets isolated (by a barrier, cave, island, etc.).

Causes a change in allele frequencies because only some of the alleles from the original population may be represented.

Genetic bottleneck

A type of genetic drift -

When there is a sharp reduction in population.

Can be caused by natural disasters, overhunting, etc.

Gene Flow (genetic flow)

Migration of a species into another. Movement of alleles that make two populations more similar.

Can be caused by:

• Migration of individuals across populations

• Movement of gametes (e.g. pollen)

Non-random Mating

The preference for certain individuals as mates.

Sexual selection

A type of non-random mating -

Mates chosen because of their specific traits.

It’s also a subcategory of natural selection because it increases biological fitness.

Positive assortative mating

A type of non-random mating -

Individuals mate with those who are phenotypically similar to them.

Negative assortative mating

A type of non-random mating -

Individuals mate with those who are phenotypically dissimilar/different from them.

Inbreeding

A type of non-random mating -

Mating among relative which increases homozygosity.

Physical location

A type of non-random mating -

Closeness vs. distance can lead to non-random mating

Hardy-Weinberg principle

Allele frequencies will remain constant from one generation to another provided no evolutionary influences are present.

Hardy-Weinberg Equilibrium

When the actual allele/genotype frequencies match the predicted frequencies

Calculating HWE

1. Find actual genotype frequency

   a) For AA, Aa, aa —> # individuals / total # population gives actual frequencies for each genotype

2. Determine p and q

   a) p = AA + ½ (Aa)

   b) q = aa + ½ (Aa)

3. Calculate predicted genotype frequencies

   a) p², 2pq, and q²

4. Compare predicted frequencies with actual frequencies (within 3% range)

   a) If actual = predicted, population is in HWE

   b) if actual ≠ predicted, population is evolving

Speciation

The formation of new and distinct species in the course of evolution. Occurs because of the lack of gene flow

4 necessities to define a species

1. Biological species concept

2. Morphological species concept

3. Phylogenetic species concept

4. Ecological species concept

Biological species concept

Able to produce fertile and viable offspring

Morphological species concept

Set of organisms with similar morphology (look alike)

Phylogenetic species concept

Smallest group of organisms that share a common ancestor; useful for asexual organisms

Ecological species concept

Constraint that they actually have the opportunity to interbreed with each other (occupy the same niche) (no spatial or territorial barriers)

Allopatric speciation

Speciation due to geographical/locational difference

Sympatric speciation

Speciation due to sexual isolation/difference

Pre-zygotic speciation

Reproductive isolation before sperm and egg unite to form a zygote

Post-zygotic speciation

Reproductive isolation after sperm and egg unite to form a zygote

Hybrid facts

• Interbreeding between populations going through speciation

• Have reduced fitness compared to parents

• Natural selection reduces the production of them because fitness favors offspring of those who mate within their species

3 types of rock

Igneous - formed from cooling of lava

Metamorphic - formed from igneous and sedimentary rock but the crystal structure is altered by Earth’s extreme heat

Sedimentary - formed by the compression of the deposition of sands and particles of inorganic debris at the bottom of oceans/lakes. May contain fossils.

Stratigrophy

The order and relative position of rocks and how they relate to the geological time scale - applies to sedimentary rock formations.

• New layers are always on top of old layers

Problems with dating sedimentary rock formations

• Uplift - when the earth moves and the layers tilt/fold/invert

• Erosion

• Unconformities - when erosion removes layers of rock and gaps in the rock appear

Calculating rock age

age = half life x n

n = # of half lives passed = x years / y half life

1/2, 1/4, 1/8, 1/16…

exponential decay = (1/2)ⁿ = how much is left after n half lives have passed

C-14 (carbon-14) dating

• Short half life

• Can only be used on organic matter from recent past

• ¹⁴C:¹²C typical ratio

⁴⁰K:⁴⁰Ar (potassium-40 and argon-40) dating

• Long half life

• Can be used for dating ancient igneous rock

• ⁴⁰K decays to ⁴⁰Ar

• Dated by looking at ⁴⁰K:⁴⁰Ar ratio

Calculating fossil age

Fossil age = n x half life duration
n = # of half lives passed = x years / y half life

If given (1/2)ⁿ = z, calculate how many times ½ was multiplied by itself to get to z to find n

Things continental drift affects

• Atmospheric circulation of air

• Oceanic circulation of water

• Climate

• Sea level

• Amount of shoreline habitat

When the first evidence of life on earth was

3.5-3.8 billion years ago

When oxygenic photosynthesis arose in Cyanobacteria

2.7 billion years ago

Cyanobacteria were first to produce oxygen as a toxic byproduct

When the origin of eukaryotes was

1.5-1.8 billion years ago and oxygen also began accumulating

Endosymbiotic theory

Eukaryotic cells originated when ancestral prokaryotic cells engulfed bacteria, forming mitochondria and chloroplasts

When the Cambrian explosion was

542 million years ago - rapid evolutionary diversification of life and an increase in oxygen to almost present day levels

Order of Earth milestones

1. Origin of life on Earth

2. Evolution of oxygenic photosynthesis

3. Origin of eukaryotes

4. Cambrian explosion

Evolutionary radiations/Adaptive radiations

Periods of increasing biodiversity and rapid speciation

• Often occur after mass extinctions due to sudden availability of pre-occupied spaces

• Could also be due to novel adaptation that allows the exploitation of a new niche

When the End-Cretaceous extinction was

65 million years ago

• Loss of all non-avian dinosaurs

• Hypothesized causes:

  • Volcanic eruption

  • Drop in sea levels

  • Bolide impact (meteor/comet strike)

Oparin-Haldane hypothesis and requirements for the origin of life

1. Carbon source (organic molecules)

2. Energy

3. Segregate molecules from environment

4. Hereditary mechanism

Miller-Urey experiment

Experiment that simulated hypothetical early earth with a reducing atmosphere, ocean, and a hydrologic (water) cycle. After a week, the apparatus organic molecules such as amino acids.

Ways the first organic molecules could have come to earth

• Comets

• Atmospheric production

• Thermal vent production

Oparin-Haldane hypothesis

Suggests life on earth began because:

Formation of organic molecules —> formation of polymers —> formation of protocells

1. Organic molecules form from inorganic molecules

   a) can occur spontaneously (Miller-Urey experiment)

   b) ex. animo acids, nitrogenous bases (part of RNA/DNA)

2. Macromolecules polymerize

   a) minerals and clays acting as template

   b) ex. proteins, nucleic acid

3. A hereditary mechanism develops

   a) RNA as both enzyme and genetic material

4. Membrane-enclosed protocells form

   a) can occur spontaneously under lab conditions

RNA

A molecule in cells that helps turn DNA into proteins.

When individual nucleic acids polymerize, giving this, with complex 3-D structures. Most common are hairpins, formed when a single strand folds back on itself.

Provides a template that can be copied (heritable information transfer)

Ribozymes

RNA molecules that act like enzymes - Catalytic RNAs. Enough structural and chemical complexity to catalyze simple chemical reactions. RNA is capable of encoding genetic information and enzymatic activity. Self-replicating RNA has evolved in labs.

RNA World hypothesis

• RNA predated DNA, first hereditary mechanism

• Became hereditary mechanism allowing protocells to be self sustaining

• Ribozyme - can catalyze simple reactions and self replicates

Protocells

Spontaneous forming lipid membrane with organic molecules and polymers inside - the beginning of our first cells

ex. liposomes