Classification by Aristotle and Theophrastus

E arly C lass ifica tion

P lan ts A n im a ls

L ivin g Th in g s

Classification by Aristotle and Theophrastus

A ris to tle 's C lass ifica tion

A ir D w e lle rs L an d D w e lle rs W ater D w e lle rs

A n im a ls

Classification by Aristotle and Theophrastus

Th eop h ras tu s 's C lass ifica tion

H erb s(so ft s tem )

S h ru b s(S evera l w od d y s tem s)

Trees(s in g le w ood y s tem )

P lan ts

How the 6 kingdoms came about• At first, only two

kingdoms were recognized

• Then 5 kingdoms (where protists had both plant & animal qualities)

• And now there are 6 kingdoms, organized into 3 domains

6 Kingdom Classification

Kingdom Classification

• Organisms are classified based upon 4 main criteria:– Does it have a nucleus? Is it Prokaryotic or

Eukaryotic?– Is it Unicellular (one cell) or multi-cellular (more

than one)?– How it gets food? Is it autotrophic or

heterotrophic?– Movement – Is it motile or non-motile?

Monera – Eubacteria - Bacteria

Kingdom Bacteria - Characteristics

• Nucleus?– All are Prokaryotic

• Cellular Structure?– Most are unicellular – some colonize– Usually classified according to shape, cell wall

and nutrition.• cocci (round-shaped), bacilli (rod-shaped), and

spirilli (spiral-shaped)• Nutrition?

– may be photosynthetic, chemosynthetic, or feed by absorption.

• Reproduction?– Asexual reproduction through Binary fission.

Bacterial Cells

Bacterial Shape

Gram Positive (purple) vs. Gram Negative (Pink)

+’ve have a thick peptidoglycan cell wall

Asexual Reproduction byBinary Fission

1. DNA is replicated to make two (2) complete copies.

2. The bacterial cell increases in size and the identical copies of the DNA are moved to opposite ends of the cell.

3. A septum (dividing wall) begins to form between the chromosomes.

4. When the wall is completed the original parent cell has now been separated into two new daughter cells.

• This process takes as little as 20 minutes to complete. So one cell can become 30 000 in 5 hours.

Prokaryotes have a single, circular chromosome rather than the sets of chromosomes found in the more familiar eukaryotes, mitosis does not occur in prokaryotes. Instead, most replicate via a process of binary fission.

Replication

Conjugation

• ‘Sexual reproduction’ by bacteria.– Bacteria join through a pili

that allows genetic information to transfer from one cell to another.

– Plasmids are small loops of DNA separate from the main DNA that can move from cell to cell sharing its’ genetic information.

Not All Bad

• Many people only consider bacteria to be the cause of illness and death.

• But there are beneficial bacteria:– in your intestine, they help digest food.– in cow stomachs to help them digest grass.– in yogurt and cheese, it curdles the milk.– Cyanobacteria are believed to be the first organisms to perform

photosynthesis. They released oxygen as a waste product, and thus changed the composition of our atmosphere, and set the stage for other forms of life.

– Other cyanobacteria are capable of fixing nitrogen into nitrates, an essential part of the nitrogen cycle.

– Bacteria and algae live in symbiosis to form lichen, a major food source for caribou.

Bacterial Resistance• Antibiotics stop bacteria in a number of ways. They

can prevent cell wall growth, some kill the bacteria directly and others prevent it from reproducing.

• Over time, bacteria mutate and evolve new strains resistant to antibiotics that attack them.

• Plasmids can then be used to pass this resistance on to neighbours.– if an antibiotic kills 99.9% of bacteria, the 0.01% that is not

affected can grow, and flourish.• Antibiotic resistance is becoming a growing concern

in our healthcare system.

Kingdom Archaea

• Very similar in appearance to ‘eubacteria’; however, the composition of the cell walls and nucleic acids may be drastically different.

Types

– Methanogens- live free of O2 and break down inorganic compounds like H2S (hydrogen sulfide) and releases methane (CH4) as a waste product.

• Halophiles- salt-loving bacteria

• Thermoacidophiles- archaea bacteria that love and flourish in acidic or extreme temperatures.

• Do Page 139:• #1, 2, 3, 4, 7, 8 and 9

Protista

Kingdom Protista - Characteristics

• Nucleus?– All are Eukaryotic

• Cellular Structure?– Most are unicellular

• Nutrition?– may be photosynthetic, may feed by absorption,

or may ingest food.

• Reproduction?– Both Sexual and Asexual means of reproduction

Classified according to nutrition

• There are three groupings for Protists (so far)– Protozoa (animal-like protists) : heterotrophs that

ingest or absorb food.– Algae (plant-like protists) : autotrophs that carry

out photosynthesis.– Slime moulds and Water moulds (fungus-like

protists) : heterotrophic• Read pg 140

Protozoa (Animal-like Protists)

• Meaning ‘first animals’• Feed on other organisms, living or dead.• Complex structures and reproduction

Life Cycle – See Page 146

• Plasmodium vivax a Sporozoan human parasite is responsible for one type of malaria.– A mosquito bites an infected person, ingesting the P.

vivax cells.– The gametes (reproductive cells) fuse to form a

(diploid) zygote inside the gut of the mosquito. The zygote divides many times producing many spore-like structures (sporozites) that become released.

– The sporozoites invade the salivary glands of the mosquito, and are injected into a new host while the mosquito feeds.

– Once inside the host (human) sporozoites will reproduce asexually in the liver to form another spore-like cell. These cells then leave the liver and invade red blood cells, where they reproduce many times.

– Red blood cells rupture, releasing toxic substances and more spores that infect neighboring RBC’s.

Algae (Plant-like Protists)

• Simple, aquatic, chlorophyll-containing organisms.

• Photosynthesizes • Ranging in size from single

celled entities to giants 60 meters long (seaweeds).

Slime/Water Moulds (Fungus-like)

• These are difficult to classify. They have characteristics of fungus, plant and protozoa at the same time.

• These cute guys make great pets!!!

Fungi

Kingdom Fungi

• Most multicellular, some are unicellular (Yeasts).

• Eukaryotic cell structure• Absorptive Heterotrophs• Non Motile

Multi-cellular Structure

• The bodies are made up of a network of fine filaments called Hyphae. The bulk of a Fungus is under the soil as a branching network of hyphae called a mycelium. – Hyphae can appear as either large loosely branching

multinucleated cells or divided into individual cells with walls (Septa)

• Fungi do have cell walls, but they are made with chitin, a material similar to the external skeleton of insects.

Nutrition

• All are heterotrophs, and most are saprophytes (organisms that break down dead matter).

• Fungus release digestive enzymes from their mycelium and absorb the digested nutrients in through the root system. This digestion takes place outside the organsim, so it is referred to as extracellular digestion.

Reproduction

• Fungi have both asexual and sexual means of reproduction.

• Asexual methods:– Fragmentation – a piece of hyphae breaks off and

grows a new mycelia.– Spore formation – many fungi produce spores to be

carried by animals or wind to new locations. Spores can grow directly into a new organsim.

– Budding – a yeast cell reproduces by budding off the original parent. See page 157

Zygomycota

• You have seen this mold anytime you have found a piece of stale bread.

• The small black dots you may have seen are their reproductive structures

• Like bacteria this group of fungi can perform sexual reproduction when conditions are unfavourable. They produce zygospores, which is where it gets its’ name.

Life cycle of Rhizopus stolonifera

• Rhizopus have two types of hyphae:– Stolons – which spread out over the surface.– Rhizoids – penetrate deep to anchor the mold and are

used for food absorption.

• Hyphae can also be two mating types, either a + or – strand. Two haploid (having only half the number of chromosomes) hyphae of opposite mating strands fuse to form a dilpoid (having the full number of chromosomes) zygospore.

• A thick wall develops around the zygospore to protect it from damage, and it will remain dormant until conditions are favorable for growing again.

• When conditions are right the zygospore will absorb water and reproduce asexually into a third form of hyphae called a sporangiophore that projects upwards, carrying on it many sporangia (spore-bearing capsule).

• Asexual spores develop inside the sporangia and are released when the capsule splits open.