Lab 4: Life on the Cellular Level

3 domains of life

• bacteria

• archaea

• eukarya

bacteria

single-celled organisms

archaea

prokaryotic single-celled organisms that usually are extremophiles

eukarya

organisms w/ eukaryotic cells

horizontal gene transfer (HGT)

genetic material is transferred between organisms without the need for reproduction

• transformation

• transduction

• conjugation

• gene transfer agents

transformation

naked DNA uptake by bacteria

transduction

genes transferred by virus

conjugation

genes transferred between two bacteria via pilus

gene transfer agents (GTA)

virus-like particles, transfer random genomic sequences from one prokaryote species to another

which of the 3 domains of life has a nucleus?

eukarya

which of the 3 domains of life has a mitochondria/chloroplast?

eukarya

which of the 3 domains of life has peptidoglycan?

bacteria

which of the 3 domains of life has branched membrane lipids?

archaea

which of the 3 domains of life commonly has introns in genes?

eukarya

how are chromosomes shaped in eukarya?

linear

how are chromosomes shaped in bacteria and archaea?

circular

theory of endosymbiosis

• mitochondria resulted from the engulfment of aerobic bacteria

• chloroplasts resulted from the engulfment of cyanobacteria

domain archaea

• more closely related to eukarya

• many but not all live in extreme environments

domain bacteria characteristics

• most widespread and abundant organisms on Earth

• many ways to classify

  • cell shape

  • oxygen requirements

  • cell wall structure

  • unique features and ability to transfer plasmids

domain bacteria cell shape

• bacillus

• coccus

• spirillus

bacillus shape

rod-shaped

coccus shape

spherical or round shape

spirillus shape

spiral or helical

bacteria oxygen requirements

• aerobic: require oxygen

• anaerobic: cannot tolerate oxygen

• facultative anaerobes: prefer oxygen, but can survive without it

bacteria cell wall structure

• gram +

• gram -

bacteria unique features

cell wall of peptidogylcan:

• layer of polysaccharides crosslinked with peptides

• thick in gram + bacteria

• thin in gram - bacteria, often with a secondary outer membrane

bacteria ability to transfer plasmids

HGT

• plasmids contain extra genetic material not found in the bacterial chromosomes

• can give new capabilities to bacteria

Cyanobacteria

• performs photosynthesis

• some have nitrogen-fixers cells called heterocysts

• may survive harsh environments through the production of spore-like cells called akinetes

• cylindrospermum

what are the nitrogen-fixer cells in cyanobacteria called?

heterocysts

what does akinetes (spore-like cells) aid cyanobacteria with?

surviving through harsh environments

what is the cyanobacteria we observed?

cylindrospermum

single-celled members of domain eukarya (protists) characteristics

• have membrane bound organelles and DNA contained in a nucleus

• most diverse group or organisms in terms of both structure and function

• currently organized into 4 or 6 supergroups

Supergroup Excavata (eukarya)

• some groups have an “excavated” feeding grove on their surfaces

• generally, have 2 or more flagella

Euglenozoans (Excavata)

• most are both photosynthetic and heterotrophic (mixotrophic)

• 2 flagella originating from within an infolded structure

• stigma (eyespot): photosensitive organelle

• flexible protein pellicle allows shape changes

• Euglena

supergroup Archaeplastida (eukarya)

• includes multicellular plants, red, and green algae

• photosynthetic

• fix CO2, store carbohydrates as starch, and have cellulose in their cell walls

Chlorophytes (Archaeplastida)

• Chlamydomonas

• Volvox

• Spirogyra

Chlamydomonas (Chlorophyte)

• unicellular chlorophyte

• pear-shaped morphology

• 2 anterior flagella

Volvox (Chlorophyte)

more complex and colonial

Charophytes (Archaeplastida)

closest living relatives to land plants and resemble them in morphology and reproductive strategies

• Spirogyra

Supergroup “SAR”

3 groups

• stramenopiles

• alveolates

• rhizarians

stramenopiles (SAR)

typically have 2 flagella: one “hairy” and the other “smooth” (include true kelp - multicellular brown algae)

• Saprolegnia

• Diatoms

Saprolegnia (Stramenopiles)

• parasitic

• grows into hyphae similar to fungi

• structure called an oogonium

Diatoms (Stramenopiles)

• cell wall composed of hydrated silica plates

• carbohydrates stores as laminarin

Alveolata (SAR)

• have membranous sacs underneath the cell membrane called alveoli

• flagellum

Dinoflagellate (Alveolata)

2 flagella in grooves, causes characteristics whirling motion

• Peridinium

Ciliates (Alveolata)

uses many cilia to move

• blepharisma

Rhizarians (SAR)

• most members to employ psuedopoedia

• mineralized test shell

• composed by 2 subgroups

  • Foraminifera

  • Radiolaria

Foraminifera (Rhizarians)

• possess a multi-chambered shell - still one cell

• shell made of calcium carbonate

Radiolaria (Rhizarians)

• spherically or radially symmetrical

• shell made of silica

Supergroup Unikonta

• generally have no set growth form

• generally have a single flagellum

• includes Nuclearids, Kingdom Fungi, Choanoflagellates, and Kingdom Animalia

Amoebozoans (Unikonta)

• very large single-celled organisms

• no test/shell or cell wall present

• lobe-shaped or tubular pseudopodia (mobility and food capture)

Opisthokonts (Unikonta)

characterized by a single, posterior flagellum on flagellated cells

Rotifers (Opisthokonts)

Kingdom Animalia Phylum Syndermata:

• Corona is a two-part ciliated structure around the mouth

• advanced animal with a nervous system and other organ systems

• smaller than some of the single-celled organisms we have seen today