6 Kingdom Classification

Kingdom Classification

• Organisms are classified based upon 4 main criteria:

– How it gets food? Is it autotrophic or heterotrophic?

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

– Does it have a nucleus? Is it Prokaryotic or Eukaryotic?

– Movement – Is it motile or non-motile?

Kingdom Monera

• Most are unicellular – some colonize

• All are Prokaryotic

• Usually classified according to shape, cell wall and nutrition. – cocci (round-shaped), bacilli (rod-shaped), and

spirilli (spiral-shaped)

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

• Asexual reproduction through Binary fission.

Bacterial Shape

Gram Positive (purple) vs. Gram Negative

(Pink)

+’ve have a thick peptidoglycan cell wall

Reproduction - Binary Fission

• 1. As bacterial cell grows, it duplicates its’ nucleic acid.

• 2. The cell elongates and the chromosome divides.

• 3. A cell partition or septum forms between the chromosomes.

• 4. The septum completes itself and distinct walls form.

• 5. The cell separates into two new cells.

• This process takes as little as 20 minutes. 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.

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.

– 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.

Kingdom Protista

• Most are unicellular

• Eukaryotic

• may be photosynthetic, may

feed by absorption, or may

ingest food.

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

reposible 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!!!

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 of 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.