Download Kingdom Bacteria: Bacteria are simple, prokaryotic organisms. They

Kingdom Bacteria:
Bacteria are simple, prokaryotic organisms.
They can be classified according to shape:
i)cocci (round)
ii) bacilli (rod-shaped) and
iii) spirilli (spiral-shaped).
Bacterial cells reproduce by means of asexual reproduction (one parental
cell gives rise to 2 or more identical offspring). It is the process of
binary fission in bacterial cells.
Example of Reproduction for Eubacteria and Archaebacteria
The bacterial cell, (example used: E. coli), reproduces by binary fission.
(See Figure 5.4, p. 134).
1. As the bacterial cell grows, it makes a copy of its original, single
chromosome.
2. The cell elongates and separates into the two chromosomes.
3. Cell partition or septum forms between the two chromosomes.
4. The septum completes itself and distinct walls form.
5. The cells separate and two new cells are produced.
This process takes as little as 20 minutes. One cell can become 30 000 in
5 hours.
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. The can prevent cell wall
growth, some kill the bacteria and others prevent it from making more DNA
or RNA. Over time, bacteria exposed to antibiotics evolve new strains
resistant to them. If an antibiotic kills 99.9% of bacteria, the 0.01%
that is not affected by it can grow, and flourish. Antibiotic resistance
is a major concern in our healthcare system.
Kingdom Protista:
Protists are microscopic, eukaryotic organisms. They are classified into
three major groups according to their type of nutrition.
The groups are:
1) Protozoa (animal-like protists) : heterotrophs that ingest or absorb
food. Eg. Amoeba and Paramecium
2) Algae (plant-like protists) : autotrophs that carry out photosynthesis.
Eg. Kelp and red algae (Rhodophyta). Kelp do not have true stems, roots or
leaves, and a whole organism can be grown from a fragment of kelp.
3) Slime moulds and Water moulds (fungus-like) : heterotrophic.
Example of a Protist Life Cycle: (See Figure 5.15, p. 146).
Plasmodium vivax (a human parasite), is responsible for one type of
malaria in humans.
(Note - a “zygote” is formed when two reproductive cells combine. Eg. A
sperm and egg combine to make a zygote before division takes place)
1. A mosquito bites an infected person and ingests the reproductive cells
of the Plasmodium present in red blood cells.
2. The gametes (reproductive cells) fuse to form a (diploid) zygote inside
the gut wall of the mosquito and divide many times to form numerous sporelike fragments or sporozoites. The zygote breaks open releasing the
sporozoites (spore cells).
3. The sporozoites migrate and invade the salivary glands of the mosquito.
From here, they will be injected into a new human host when bitten by the
mosquito.
4. Once inside the new human host, sporozoites will reproduce asexually in
the liver to form a second type of sporelike cell. The cells leave the
liver and enter the bloodstream where they invade red blood cells. Once
inside the red blood cells, they multiply at a very rapid rate.
5. Red blood cells rupture releasing toxic substances and spores. These
spores infect other red blood cells. The cycle repeats itself when a
mosquito bites the infected person.
Kingdom Fungi:
Fungi are non-photosynthetic heterotrophs that grow in the ground and
possess cell walls. Examples include moulds, mildews, mushrooms,
toadstools, and yeasts.
The cell walls are composed of chitin, like external skeletons of insects.
The bodies of fungi are made up of a network of fine filaments called
hyphae (singular hypha). Many hyphae can clump together to form
mycelium. Most of the hyphae are underground, or buried in the object it
is digesting. They release digestive enzymes, and absorb the nutrients all
through a process called extracellular digestion.
The hyphae can be buried deeply in the object, it is therefore unwise to
simply cut off the mould and eat what is left. (Exception - cheese)
Fungi can be extremely poisonous and deadly. Others can be beneficial,
including penicillin, blue cheese mould and yeast.
Fungi are classified according to their reproductive characteristics.
They are:
1) Zygomycotes — zygospores — sexual reproduction.
2) Basidiomycotes — basidiospores — sexual reproduction.
3) Ascomycotes — asci (spores spread by wind) — sexual reproduction.
4) Deuteromycotes — conida — asexual reproduction.
Example of a Fungus Life Cycle : (See Figure 5.28, p. 154).
Rhizopus stolonifera is the common black bread mould. It belongs to the
phylum Zygomycota.
Asexual reproduction: The most common form of reproduction.
A special kind of hyphae called sporangiophores grow upward bearing
the sporangia (spore filled capsules)
The small black dots or fuzz on bread are the asexual reproductive
structures of the bread mould.
The black spores are released when the sporangia breaks open. The
spores will grow new hyphae and develop into a new crop of mould.
Sexual reproduction:
Bread mould will reproduce by sexual reproduction when times are
unfavorable.
During sexual reproduction, two regular hyphae of opposite types (+
and - mating strains) fuse to form a zygospore. (Where the phylum
name comes from).
A thick wall develops around the zygospore for protection.
The zygospore will remain dormant until conditions are favorable for
growth.
Once this happens, the zygospore will absorb water and the nuclei
will undergo meiosis to produce a sporagium (singular of sporangia),
which will release spores the same as asexual reproduction.