Transcript Unit Two: Biodiversity

Unit Two: Biodiversity
Chapter Five and Six
Understanding Organisms
Kingdom Bacteria
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Bacteria are simple, prokaryotic organisms.
They can be classified according to shape:
Cocci (roundshaped);
Bacilli (rod-shaped) and
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. (p. 134 - 135)
Example of Life Cycle of
Eubacteria and Archaebacteria
The bacterial cell, (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.
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.
• 2) Algae (plant-like protists) : autotrophs that
carry out photosynthesis.
• 3) Slime moulds and Water moulds (funguslike) : heterotrophic.
Major Protista Groups
Protozoan
include the
phyla
Algae
contains the
following
phyla
Green Algae
Sarcodines
Amoeba
Ciliates
Foraminifera
Slime Moulds
and Water
Moulds
Diatoms
Flagellates
Trypanosoma brucei
Paramecium
Example of a Protist Life Cycle :
(See Figure 5.15, p. 146).
• Plasmodium vivax (a human parasite), a Sporozoan
(Phylum Sporozoa), is responsible for one type of
malaria in humans.
• 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 spore-like
fragments or sporozoites. The zygote breaks open
releasing the sporozoites (spore cells).
Example of a Protist Life Cycle :
(See Figure 5.15, p. 146).
• 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 spore-like 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.
• They have some plant-like qualities.
• The bodies of fungi are made up of a network of
fine filaments called hyphae (singular hypha).
• A loose, branching network of hyphae that
makes up the bulk of a fungus is called a
mycelium.
Types of Fungi
• Fungi are classified according to their
reproductive characteristics.
• 1) Zygomycotes — zygospores — sexual
reproduction.
• 2) Basidiomycotes — basidiospores — sexual
reproduction.
• 3) Ascomycotes — asci (spores spread by wind)
— sexual reproduction.
• 4) Deuteromycotes — conida — asexual
reproduction.
Rhizopus stolonifera
Ascomycota - Morels
Mushroom - Basidiomycota
Deuteromycota – Fruit moulds Pennicillium
Example of a Fungus Life Cycle
(See Figure5.28, p. 154).
• Rhizopus stolonifera is the common black bread
mould.
• The small black dots or fuzz on bread are the
reproductive structures of the bread mould.
• The bread mould reproduces by asexual
reproduction, but can also reproduce by sexual
reproduction when times are unfavorable
(producing zygospores).
• These are diploid cells that contain two copies
of every chromosome.
• Rhizopus belongs to the Phylum Zygomycota or
the zygospore fungi.
Sexual Reproduction Phase
• The zygospores develop after two haploid
(monoploid) hyphae of opposite types (+ and mating strains) combine and fuse together to
form the zygospores.
• The bread mould is made up of two forms of
hyphae.
• The horizontal hyphae are the stolons and the
downward growing hyphae are the rhizoids.
• The stolons spread out over the surface of the
bread while the rhizoids anchor the mycelium to
the bread surface.
Sexual Phase (continued)
• The rhizoids secrete enzymes that digest
the food (the bread) and then absorb the
digested nutrients.
• A thick wall develops around the
zygospore for protection.
• The zygospore will remain dormant until
conditions are favourable for growth.
• Once this happens, the zygospore will
absorb water and the nuclei will undergo
meiosis.
Asexual Reproduction Phase
• The bread mould will develop
sporangiophores, a third form of hyphae.
• The sporangia or spore-bearing
capsules are located at the ends of the
sporangiophores.
• The asexual spores develop inside the
sporangia and are released when the
capsules split open.
Kingdom Plantae
• Botany is the study of plants. All plants
are said to have a common ancestor; (ie.)
it is thought that plants have evolved from
an ancient group of green algae. Plants
and green algae share a common
evolutionary ancestry.
The general characteristics of
plants are the following :
• I) photosynthesis
• II) ability to absorb water and nutrients
• III) ability to conserve water and reduce
the drying effect of air
• IV) process of gas exchange
• V) presence of supporting tissues
• VI) ability to reproduce
Major types of Plants
• Plants can be classified according to the
presence or absence of vascular tissue.
• Vascular tissue is the tissue that supports
water and the products of photosynthesis
throughout a plant.
• Plants lacking vascular tissue are called
bryophytes.
• Plants which have vascular tissue are
called tracheophytes.
Vascular tissue
• Vascular tissue is made up of xylem and
phloem cells.
• Xylem carries water and minerals to the
leaves of plants.
• Phloem transports food synthesized in
leaves throughout the plant.
Cuticle and Stomata
• Land plants have a cuticle and stomata
(sing. stoma) present.
• A cuticle is a noncellular layer secreted by
epidermal cells which helps to protect cells
from drying out.
• Stomata are pores in the epidermis of a
plant, particularly the leaves, which permit
the exchange of gases between the plant
and the air aroundit
Classification system (land plants) :
• Nonvascular (Bryophytes)
– eg. mosses, liverworts, hornworts
• Vascular (Tracheophytes)
Seedless (Spores) (Spore-bearing plants)
– eg. whiskferns, club mosses, horesetails, ferns
Seed (embryo + stored food + tough water proof
coat or seed coat)
– Gymnosperms (cone-bearing plants) : conifers.
– Angiosperms (flowering plants) : classified into two
groups according to number of seed leaves or
cotyledons on the embryo within the seed —
monocots (one seed leaf) and dicots (two seed
leaves).
BRYOPHYTES
(Phylum Bryophyta)
• Bryophytes are nonvascular land plants that are
small in size and grow close to the ground.
• Examples would be mosses, liverworts and
hornworts.
• They reproduce by alternation of generations; a
two part life cycle with alternating monoploid (n)
and diploid (2n) phases.
• For bryophytes, the dominant part of the life
cycle is the gametophyte generation (what is
actually seen). (See Figure 6.3, p. 166).
Bryophytes Characteristics :
• 1. They lack specialized tissue that transports
water as in vascular plants. There is a problem
of dessication or drying out in these plants.
• 2. They lack true roots, stems and leaves and
are anchored to the ground by structures called
rhizoids. A rhizoid is a simple structure (other
than a true root) which doesn’t channel water to
other parts of the plant.
• 3. They require water for sexual reproduction.
Water is needed for fertilization to occur. Sperm
must swim through water in order to reach the
egg.
TRACHEOPHYTES
(Phylum Tracheophyta):
• Tracheophytes are “true” terrestrial plants.
• Examples would be ferns, herbs, shrubs, trees
and flowering plants.
• They are vascular plants and have vascular
tissue.
• These are modern-day plants and the
sporophyte generation is predominant.
• Some tracheophytes are spore-producing
vascular plants; such as whiskferns, club
mosses, horesetails and ferns.
TRACHEOPHYTES
Characteristics
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• 1. They are vascular plants having
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specialized conducting tissue;
xylem(water) and phloem (food).
2. Means of reproduction:
a.) spores - club mosses, horsetails , ferns
b.) seeds - flowering plants, conifers
(Note: All spore bearing vascular plants
require water, which reflects their aquatic
ancestry.)
TRACHEOPHYTES
Characteristics
• 3. Dominant phase in the life cycle is the
sporophyte generation (larger than
gametophyte) ; gametophyte generation is very
small, only mm in length. (Note : This is an
evolutionary trend.)
• 4. Evolution of the reproductive cycle is such
that water is not an essential requirement for
reproduction. It enables plants to survive in a
terrestrial environment. This allows for greater
adaptability and less dependence on a wet
environment (like the bryophytes).
Diversity and success of the
Angiosperms
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The angiosperms are the flowering plants and are the
most diverse plant group. This diversity is due to a
variety of factors, such as:
the assistance of animals and wind in pollination;
the presence of structures in plants specific to
attracting certain animal pollinators whom the plants
supply with food;
the way seeds are protected;
the function of fruits in seed dispersal, and
the presence of specialized tissues in plants to help
them survive heat, cold, and droughts.
READ pp. 174 – 181 for details. You will be responsible for this!
Example of the Fern Life Cycle as
a representative (seedless) plant:
(See Figure 6.9, p. 173).
• 1. A sporangium produces haploid
(monoploid) spores that germinate to form
a gametophytecalled a prothallus.
• 2. The prothallus produces antheridia
(male organs) and archegonia (female
organs).
• 3. Sperm swim through a droplet of water
to an egg produced by the archegonium.
Fern Life Cycle (continued)
• 4. The fertilized egg begins to grow into a
sporophyte.
• 5. The sporophyte matures and roots and
fronds develop out of the growing rhizome.
• 6. Sori develop on the pinnae. Spores are
formed in the sori by meiosis.