Bio Term Test 1

How old is Earth?

4.6 billion years old

When did the First Life Forms Appear on Earth?

3.8 billion years ago

How did Life Arise?

1. Abiotic synthesis of small organic molecules

2. Joining of these small molecules

3. Packing of the molecules into protocells

4. Origin of self replicating molecules (RNA)

What were the First Catalysts?

Ribozymes (RNA)

RNA both helped in self replicating and catalyzing

Early Atmosphere

It was a reducing environment (as opposed to an oxidizing atmosphere)

These conditions favored a synthesis of organic compounds

Soup Analogy

Ingredients = Oparin and Haldane

Oven = Energy such as lightning and UV radiation

Miller and Urey

They provided conditions similar to earths early atmosphere and tested the Oparin-Haldane hypothesis

Simulated conditions in a lab

Produced amin acids

What does the Fossil Record Reveal?

It reveals the changes in history of life on earth and it shows the kinds of organisms on Earth overtime

Sedimentary Rocks

Deposited into layers called strata and are the richest source of fossils

Where are Older Fossils?

Older fossils are farther down in the earth

Newer ones are nearer the top

Stromatolites

The oldest known fossils

They are rocks formed by the accumulation of sedimentary layers on bacterial mats

They are layers of single cell organisms on top of each other

When do Stromatolites date back to?

3.5 billion years ago

How long were Prokaryotes the only Inhabitants of Earth?

1.5 billion years

Oxygen Revolution

O2 accumulated gradually in the atmosphere from about

2.7 to 2.4 billion years ago

Proof of Oxygenic Revolution

Branded iron formation of rocks

The iron reacted with the oxygen to rust

Consequences of the Oxygenic Revolution

Many prokaryotic groups could not adapt to increased atmospheric O2 levels

Some groups survived and adapted using cellular respiration to harvest energy

When do the Oldest fossils of Eukaryotes Date back to?

1.8 billion years ago

Endosymbiont Theory

The theory proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living with in larger host cells

Endosymbiont

A cell that lives within a host cell

Serial Endosymbiosis

Mitochondria evolved before plastids through sequence of endosymbiotic events

ATP for the host cell was the rent that the mitochondria paid

Evidence of the Endosymbiotic Theory

Have two membranes

Utilize electron transport enzyme

Has its own DNA

Have ribosomes

Prokaryotic Ribosome

50S subunit

30S subunit

70S ribosome

Eukaryotic Ribosome

60S subunit

40S subunit

80S ribosome

When did the Second Wave of diversification Occur?

When the multicellularity evolved and gave rise to algae, plants, fungi, and animals

Cambrian Explosion

The sudden appearance of fossils resembling modern animal phyla in the Cambrian period (535-535 millions years ago)

When was the Land Colonized?

Fungi, plants and animals began to colonize land about 500 million years ago

What Evolved from lobe-finned Fish and When?

Tetrapod’s about 365 millions years ago

What Evolved from Tetrapod’s and When?

The human lineage evolved around 6-7 million years ago

When did Modern Humans Originate?

195,000 years ago

What does the Rise and Fall of Groups of Organisms Reflect?

It reflects the differences in speciation and extinction rates

What can Extinction be Caused by?

Can be caused by changes to a species biotic and abiotic environment

Mass Extinction

The rate of extinction is increased dramatically

Adaptive Radiation

The rapid evolution of diversity adapted species from a common ancestor

What May Adaptive Radiation Follow?

Mass extinctions

The evolution of novel characteristics

The colonization of new regions

Taxonomy

Ordered division and naming of organisms

Linnaeus (18th Century)

Published a system of taxonomy based on resemblances

2 Key Features of Linnaeus’s System

1. Utilize binomial nomenclature: Genus + Specific epithet

2. Utilizes Hierarchal classification

Taxonomic Groups from Broad to Narrow

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Taxon

A taxonomic unit at any level

Phylogeny

Evolutionary history of a species or group of related species

Systematics

Classifies organisms and determines their evolutionary relationships

Use fossil, molecular, and genetic data to infer evolutionary relationships

What does Phylogenetic Tree Represent?

It represents a hypothesis about evolutionary relationships

Branch Point (Node)

Divergence of two species from a common ancestor

Sister Taxa

Groups that share an immediate common ancestor that is not shared by any other group

Sisters not cousins

Rooted Tree

Includes a branch to represent the last common ancestor of all taxa in the tree

Basal Taxon

Diverges early in the history of a group and originates near the common ancestor of the group

Polytomy

A branch from which more than two groups emerge

What do Phylogenetic Trees Show?

Pattern of descent

What do Phylogenetic Trees not Show?

When or how much genetic change has occurred in a lineage

Can Taxa be Rotated Around Nodes and still Depict the same Relationships?

Yes

Monophyletic Group

Consists of all the descents of a single common ancestor

Paraphyletic Group

Consists of some, but not all descendants of a single common ancestor

Polyphyletic Group

Does not include the common ancestor of all descendants (excludes at least one monophyletic group)

3 Ways of Making a Phylogeny

1. Character Table

2. Phylogenetic tree

3. DNA

How to Make a DNA Phylogeny?

Start with the first hypothesis

Map all the changes onto the tree and count the number of events

Do the same for other Phylogenetic hypothesis

The tree with the fewest number of events is the best tree

The first tree is the most parsimonious

Parsimony

The fewest number of evolutionary steps

Phylogenetic Bracketing

Allows for us to predict features of an ancestor from features of its descendants

What are the Best Hypotheses for Phylogenetic Trees?

The trees that fit the most data:

Morphological, molecular, and fossil

How Many Kingdoms did Early Taxonomists Have?

2

Plants or animals

The 5 Kingdoms

Monera (prokaryotes)

Protista

Fungi

Plantar, and Animalia

Monera

Archaea and bacteria prokaryotes

Small

Lack internal Organelles

Simple genetic information

Important in nutrient cycling, agents of disease

Protista

Single celled eukaryotes

Most artificial of kingdoms

Have flagella and cilia

Have true organelles

Range from algae to animal- and fungal-like heterotrophs

Almost all are aquatic and aerobic

Plantae

Multicellular photosynthetic autotrophs

All terrestrial, secondary specialization -Adapts to prevent dying

Fungi

Multicellular

Heterotrophic - Obtain nutrients by absorptions

Degrade organic matter majority of lifecycle spent in haploid state

Animalia

No cell walls

Separate tissues

Cell fate is determined

Most complex organisms with many feedback and control systems

3 Domain System

Bacteria

Archaea

Eukarya

Which of the 3 Domains are more Closely related to Each other?

Eukaryotes and Archaea

What does a typical Prokaryotic Cell Contain

Fimbriae

Nucleoid

Ribosomes

Plasma membrane

Bacterial chromosome

Cell wall

Capsule

Flagella

Most Common Shapes of Prokaryotic Cells

Coccus

Bacillus

Spiral

Prokaryote Cell Wall

Peptidoglycan

Are Eukaryotes or Prokaryotes Bigger?

Eukaryotes

Capsule

A polysaccharide and/or polypeptide layer covers many prokaryotes

Sits on top of the cell wall

Viscous and gelatinous

Functions of the Capsule

Contribute to virulence

Resists drying

Resists engulfment

Enables adhesion

Streptococcus Mutans

Plaque develop and produce acid, which dissolves tooth enamel

Fimbriae

Hair like appendages that allow prokaryotes to stick to their substrate or other individuals in a colony

All over the cell

Small and thin

Solid structure

Pili

Involved in motility (gliding and twitching motility)

Conjugation pili involved in DNA transfer from one cell to another

Function of Cell Wall (Prokaryote)

Maintain cell shape

Physical protection

Prevents the cell from bursting in a hypotonic environment

Gram Positive Characteristics

Thicker peptidoglycan

No outer membrane

Purple circle

Gram Negative Characteristics

Thinner peptidoglycan

Outer membrane

Pink rod

Gram-Positive Bacteria

Alcohol dehydrates peptidoglycan

CV-I crystals do not leave

Gram Negative Bacteria

Alcohol dissolves outer membrane and leaves holes in peptidoglycan

CV-l washes out; cells are colorless

Safranin added to stain cells

Cell Wall in Eukaryotes (Plants)

Plant cells walls made of different polymers

Cellulose, hemicellulose, pectin, lignin

Cell Wall in Eukaryotes (Fungi)

Fungal cell walls made of chitin, glucans

Internal Organization in Prokaryotes

Prokaryotic cell usually lack complex compartmentalization

However some prokaryotes do have specialized membranes that perform metabolic functions

Prokaryotic Flagella

Flagellin

Used for propulsion

Have a motor (4 rings) and a hook

Allow bacteria to move toward or away from stimuli by “running and tumbling”

Fluid structure

3 Types of Taxis (Stimuli)

Chemotaxis

Phototaxis

Magnetotaxis

Monotrichous

1 flagella on 1 end

Amphitrichous

2 flagella 1 per each end

Lopotrichous

4 flagella at 1 end

Peritrichous

Flagella surrounding everywhere

Amphilophotrichous

Tuft of flagella at both ends

Magnetotaxis

Small magnets inside of bacteria used to move around

Eukaryotic Flagella

Tubulin based

9 microtubules around and 2 in the middle

Whip like motions

Prokaryotic Chromosome

DNA is in a nucleoid region

Usually a circular chromosome

Less DNA than the eukaryotic genome

DNA is supercoiled

Eukaryotic Chromosome

Large linear with several copies

Why is DNA Packaged into Chromosomes

1. Compact the DNA to fit into the cell

2. Protect the DNA from damage

3. Transmit all DNA to daughter cell when the cell divides

Extra chromosomal DNA in Prokaryotes

Bacteria can carry smaller rings of DNA called plasmids

They replicate independently and carry genes that are useful in stressful condition

Plasmid

Small circular, independent double-stranded DNA molecule

They can be frequently transmitted from one bacterium to another

Extra Chromosomal DNA in Eukaryotes

Mitochondria or the chloroplast (have their own DNA)

Endosymbiosis

Cell Division in Prokaryotes

Reproduce quickly by binary fission

Ranges from 20 minutes to 24 hours

Can have multiple copies of the plasmid in the cell

May be divided into 2 offspring by chance