General Biology II Exam 1 Review

chapter 20

Charles Darwin

Credited with the concept of natural selection - a mechanism of evolution that acts on variants within populations and ultimately leads to the evolution of different species.

Fitness

Features in organisms that increase the likelihood of survival and reproduction in a particular environment.

Three Domains of Life

Bacteria, Archaea, and Eukarya

Prokaryotic Domains: Bacteria, Archaea

What are viruses constructed of?

• A chemical complex of RNA or DNA (core), protected by a protein shell (capsid).

• Viruses are characterized by size and shape - 10 to 400 nm in diameter.

• Type of nucleic acid core - DNA or RNA.

• Cannot reproduce outside a living cell.

• Can be active or inactive, rather than living or non-living.

• Can be cultured only inside living cells.

• Viruses are known for causing infectious diseases in plants and animals: Herpes, HIV, cancer.

  Viruses lack metabolism; thus, antibiotics have no effect.

What is a phage?

Viruses that infect bacterial cells.

What is a viroid?

• Naked strands of RNA/

• Many crop diseases.

What is a prion?

• Protein molecules with a contagious tertiary structure.

• TSEs are neurodegenerative diseases that destroy nerve tissue in the brain. (They are untreatable and fatal.)

Compare lysogenic viral infection to lytic.

There are two types of bacteriophage life cycles.

The lytic cycle: Viral reproduction occurs, the host undergoes lysis, and hundreds of virus particles are released.

The lysogenic cycle: Viral reproduction does not occur immediately but may occur in the future. The virus becomes integrated into the host genome and may reenter the lytic cycle. This is known as latency, and the latent viral DNA is called a prophage.

What is a retrovirus? In what direction is genetic information transferred?

• Retroviruses - HIV, the virus that causes AIDS.

• Contain reverse transcriptase, which carries out RNA —> cDNA reverse transcription; cDNA becomes integrated into host DNA.

• Replicated as host DNA replicates. '

• HIV may remain latent for years.

• Viral DNA is transcribed; new viruses are produced.

Compare the 2 prokaryotic domains - Archaea and Bacteria

• Fully functioning cells. Means “before a nucleus”.

• Microscopic - Range in size from 1 to 10 um in length and 0.7 to 1.5 um in width.

• Abundant in air, water, and soil and on most objects.

Bacteria

The more common type of prokaryote. Most bacterial cells are protected by a cell wall. Contains peptidoglycan.

• Bacteria are commonly differentiated using the Gram stain procedure.

Archaea

Were formerly considered bacteria.

Carl Woese and George Fox discovered that the base sequence of their rRNA differs from bacteria.

• Archaea do not have peptidoglycan in their cell walls like bacteria.

• Archaea are biochemically more like eukarya than bacteria.

Archaea are now thought to be more closely related to eukarya than to bacteria.

Pili

Pili are hair-like appendages found on the surface of bacterial cells. They are thin, protein structures that extend outward from the bacterial cell, allowing for interaction with their environment.

Flagella

rotating filament that propels the cell

Slime Capsule

Also known as slime layers, they are protective structures found in some bacteria.

What is an Endospore?

A small, rounded, thick-walled, resting cell that forms inside a bacterial cell.

What is the nucleoid region of a prokaryote? How do prokaryotes reproduce?

The area of a prokaryotic cell where its DNA is located; it is not surrounded by a membrane. Prokaryotes reproduce asexually by means of binary fission.

How do bacteria exchange information?

Bacteria exchange information by horizontal gene transfer, such as conjugation, transformation, and transduction.

Conjugation

Conjugation pilus forms between two cells.

The donor cell passes DNA to the recipient cell through the pilus.

Transformation

Occurs when a cell picks up free pieces of DNA from other prokaryotes.

Become incorporated into the genome.

Transduction

Occurs when bacteriophages carry portions of bacterial DNA from one cell to another.

Serve as vectors.

Gram-positive bacteria

Retain dye and appear dark purple

Gram-negative bacteria

Do not retain dye and appear red.

• Gram-negative bacteria have a second plasma membrane that blocks antibiotic drugs, making infections difficult to treat.

Bacterial-shape Cocci

(round) shaped bacteria.

Bacterial-shaped bacilli

Rod-shaped bacteria.

Bacterial-shaped spirilla

Spiral-shaped bacteria.

Compare bacterial metabolism

• Photoautotrophs: use sunlight for energy ☀

• Chemoautotrophs: use chemicals for energy 🧪

• Heterotrophs: get energy by consuming organic matter 🍽

How are cyanobacteria related to lichens?

Cyanobacteria form lichens in association with fungi and can fix nitrogen in specialized cells called heterocysts.

• Cyanobacterial “blooms” result from pollution in lakes and

  ponds.

What are halophiles?

Salty lakes

• Require high salt concentrations for growth

What are Thermophiles?

Organisms that thrive in very hot environments.

Methanogens

Anaerobic marshes

Produce methane from hydrogen gas and carbon dioxide.

Name characteristics of protists. Why is it the most diverse of the 4 eukaryotic kingdoms?

• Classified in the domain Eukarya and the kingdom Protista

• Vary in size from microscopic algae and protozoans to kelp more than 200 m in length

• Although many protists are unicellular, they are highly complex

Most diverse kingdom - can be unicellular, colonial, or multicellular.

What does mixotrophic mean? What are the characteristics of Euglena?

Mixotrophic: An organism that can make its own food and also get food from other sources.

Some protozoans are mixotrophic

• Mixotrophs combine autotrophic and heterotrophic nutritional modes (ex., Euglena)

What organelles serve as energy centers for protists?

Mitochondria and plastids serve as energy centers for protists