Chapter 28: Microbiology

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Prokaryotes

Prokaryotes

The Prokaryotes

• The bacteria (domain Bacteria) and archaea (domain Archaea) are prokaryotes.

• Prokaryotes (“before nucleus”) lack a membrane bounded nucleus. Instead, the chromosome is in a nucleoid (false nucleus) that lacks an envelope.

• There are no membranous organelles but they do have ribosomes; prokaryotes have a cell wall that may be surrounded by a capsule.

• Some prokaryotes move by flagella, and some adhere to surfaces by means of small, hairlike appendages called fimbriae.

DNA

motility

Gram + or - stain

Generalized structure of a prokaryote

• Prokaryotes reproduce asexually by binary fission, and some can form endospores (anthrax).

• In order to accomplish genetic recombination (but not sexual reproduction) bacteria can also reproduce by: conjugation, transformation, and transduction.

Generalized reproduction of a prokaryote

binary fission conjugation

transformation

transduction

1 2

3

4

One cell passes DNA to another through a sex “pilus”

A bacteria takes up DNA from its liquid surroundings

Bacterial viruses carry portions of DNA from one bacteria to another

Endospore formation by a prokaryote

• Bacteria can “hibernate” to avoid unfavorable environmental conditons.

• Hibernation is accomplished

by saving a small portion of

their cytoplasm and a

copy of their DNA, and

letting the rest of the cell

dry out. They are then

encased by three layers

of spore coats.

When conditions are favorable they rehydrate and form a full bacterial cell again!

• Most bacteria are aerobic, requiring a constant oxygen supply for cellular respiration.

• Obligate anaerobes are unable to grow in the presence of oxygen; facultative anaerobes are able to grow in the presence or absence of oxygen.

• Bacteria are saprotrophs which externally digest organic compounds and absorb nutrients.

Prokaryotes, In General

• Bacteria are the decomposers in ecosystems.

• Some bacteria are symbiotic and live in association with other organisms.

• The bacteria that reside in the human intestinal tract are mutualistic (both benefit); commensalistic (no harm, no benefit) bacteria reside on our skin; and parasitic (only they benefit, we suffer) bacteria cause a wide variety of diseases.

• The cyanobacteria are photosynthetic in the same manner as plants.

Prokaryotes, In General

Your Basic Bacteria:• Bacteria occur in three

basic shapes:

rod (bacillus),

round (coccus),

or spiral (spirillum).

• Based on a dye test, bacteria are either Gram-positive or Gram-negative: Gram-positive bacteria have a thick layer of peptidoglycan on their cell wall; Gram-negative bacteria have a thin layer.

Prokaryotes

Domain Archaea:The Extremophiles

Domain Archaea

Adapted to extreme conditions:

1. Plasma membrane contains special lipids to tolerate super high temperatures, as well as modified

cell walls compositions.

2. Archaea are NOT photosynthetic. Most gain nutrition through “chemosynthesis”. That is, they can “eat” sulfur. Some excrete methane gas, which is a large contributor to the greenhouse effect (global warming).

3. Archaea have been found living in the great salt lake and dead sea (WAY HYPERTONIC!), hot springs or even submarinethermal vents ( over 200 degrees F!)

Chapter 29: Plants

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Prokaryotes

PLANTSANIMALS

FUNGI

PROTISTA

MONERA

Characteristics of Plants• Plants are multicellular, photosynthetic

organisms adapted to a land existence with features such as a waxy cuticle.

• Plants resemble algae in using chlorophylls(green) a and b and carotenoid(red) pigments for photosynthesis.

• But unlike algae, land must plants protect the developing embryo from drying out by creating a protective coat around them…...(ahhhh, the beginning of seeds and fruit!)

Nonvascular plants

Seedless vascular plants

Vascular plants

with seeds

• The many divisions of plants can be grouped into three main groups:

Nonvascular plants

Seedless vascular plants

Vascular plants

with seeds

“Vascular” refers to the tissues and structures thattransport water and minerals from the roots to all the

tissues.

Nonvascular plants(phylum: Bryophyta)

Seedless vascular plants(phylum: Trachophyta)

Vascular plants

with seeds(phylum: Trachophyta)

“Vascular” refers to the tissues and structures thattransport water and minerals from the roots to all the

tissues (namely, the Phloem and Xylem).

Nonvascular Plants

• PHYLUM: Bryophyta

• Nonvascular plants include the liverworts, hornworts, and the mosses.

• Nonvascular plants lack vascular tissues throughout their life cycle; they lack true roots, stems, and leaves.

• Sperm require water to swim to the egg.

Liverworts (a bryophte)• The liverwort has a flattened, lobed body known as thallus. • Rhizoids (rootlike hairs) project from the lower surface into the

soil. • Can reproduce asexually by forming gemmae, groups of cells

in gemmae cups on the upper surface of thallus.

• In sexual reproduction, umbrella-like gametophores produce

gametes (star-shaped for female, disc-like for males).

• Following fertilization, the dependent moss sporophyte consists of a foot, stalk, and a capsule or sporangium within which spores are produced by meiosis. They are dispersed by the wind.

• In the moss life cycle, antheridia produce swimming sperm that use external water to reach the eggs in the archegonia.

Mosses (a bryophyte)

Life-Style of Nonvascular Plants• Mosses are usually found in moist habitats

because the sperm are flagellated.

• However, mosses can live in shady cracks of hot, exposed rocks.

• Liverworts can only live in a moist environment.

Adaptations and Uses of Nonvascular Plants

• Sphagnum is bog or peat moss that is used to hold water in garden soil.

• Dried peat is sometimes used as fuel.

Nonvascular plants(phylum: Bryophyta)

Seedless vascular plants(phylum: Trachophyta)

Vascular plants

with seeds(phylum: Trachophyta)

“Vascular” refers to the tissues and structures thattransport water and minerals from the roots to all the

tissues.

Seedless Vascular Plants(phylum: Trachophyta)

• Vascular plants have vascular tissue: xylem (conducts water and minerals from the soil) and phloem (transports organic nutrients within the plant).

• Vascular plants have true roots, leaves, and stems.

• Waxy cuticles prevent leaves from drying out.

Seedless Vascular Plants(phylum: Trachophyta)

Ferns• Whisk ferns, club mosses, horsetails, and ferns are the

seedless vascular plants that were prominent in swamp forests during the Carboniferous period.

• Their incomplete decomposition formed much of the coal we burn today.

Whisk fern, Psilotum

Club moss, Lycopodium

Horsetail, Equisetum

• Ferns• Ferns have very large fronds (leaves) that grow

from a rhizome; ferns have vascular tissue and have true roots, stems and leaves (leaflets).

• Sporangia are within sori on the underside of the leaflets of a frond; meiosis occurs within a sporangium, producing spores.

• A windblown spore develops into a separate gametophyte, a heart-shaped prothallus, that bears both egg-producing archegonia and sperm-producing antheridia.

Fern Life-Cycle

Fern diversity

Nonvascular plants(phylum: Bryophyta)

Seedless vascular plants(phylum: Trachophyta)

Vascular plants

with seeds(phylum: Trachophyta)

“Vascular” refers to the tissues and structures thattransport water and minerals from the roots to all the

tissues.

Vascular Seed Plants• Phyllum: Tracheophyta (Contain Xylem and Phloem)

• Both gymnosperms and angiosperms disperse by seeds.

• A seed has a seed coat and contains an embryonic sporophyte and stored food that supports growth when the seed germinates.

• Gymnosperms have exposed or “naked” seeds. • In angiosperms (flowering plants), seeds are

enclosed by a fruit.

Gymnosperm diversity(naked-seed plants)

Gymnosperms• This group includes cycads, the ginkgo, and

conifers.

• Cycads are palm-like, tropical and subtropical plants that flourished during the era of dinosaurs.

• Ginkgo is planted in parks because it does well in polluted areas. Also used in Japanese art.

• Conifers are the largest group of gymnosperms and include cone-bearing pine, spruce, fir, and redwood trees.

Pine life cycle “pinecones” are female!

fertilized “pinecones” scales fly on the wind with wings!

• Life Cycle of a Conifer • The gymnosperm microspore develops into a

pollen grain which develops in a pollen cone. • The megagametophyte develops within an

ovule located on the scale of a seed cone. • Following wind pollination and fertilization that

do not require external water, the ovule becomes a winged seed that is dispersed by wind.

• Adaptation and Uses of Conifers • Conifers supply much of the wood used for

construction of buildings and production of paper. • Many valuable chemicals are extracted from resin, a

substance that protects conifers from fungi and insects.

• The oldest trees in the world, at 4,500 years old, are bristlecone pines in Nevada.

Impressive!!!! Trees can live longer than any other organism! They were around 2500BC, during the time of TROY…..Pharoh’s age!

Some trees today were around to see King Tut, Jesus, Mohammed

Angiosperms(enclosed-seeds)

• Angiosperms are flowering plants and include tropical and subtropical trees.

• All hardwood trees are angiosperms.

• Angiosperms are divided into moncots (such as the grass family) and dicots (such as the maple and rose families).

Flowering plant life cycleThe fruit you eat, is a plants ovary. The seeds inside are fertilized!

• Life Cycle of Angiosperms• Like conifers, angiosperms produce sperm and

eggs, except angiosperms do so within their flowers (instead of a pinecone).

• The ovules (eggs – usually a lot!) develops into seeds, each one consisting of a seed coat, stored food, and an embryo. The ovary and adjacent parts of the flower develop into a fruit.

• Fruits aid in seed dispersal.

• The Flower• The flower accounts for the success of angiosperms. • The flower both attracts animals that aid in pollination

and produces seeds enclosed by fruits that aid dispersal.

Summary

• Plants resemble algae in using chlorophylls a and b and carotenoid pigments for photosynthesis, BUT unlike algae, plants protect the embryo (seed) to keep it moist so that it can live on land existence.

Summary

• Nonvascular plants are low-growing and lack a means of water transport and internal support, whereas vascular plants have a system that transports water and also provides internal support.

• In nonseed plants, spores disperse the species; in seed plants, seeds disperse the species.

• In seed plants, a pollen grain transports sperm to the egg.