Unit Two: Biodiversity

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Unit Two Biodiversity

• Chapter Five and Six
• Understanding Organisms

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Kingdom Bacteria

• 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)

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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.

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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 (fungus-like)
  heterotrophic.

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Major Protista Groups
Algae contains the following phyla
Protozoan include the phyla
Slime Moulds and Water Moulds
Green Algae
Diatoms
Ciliates
Sarcodines
Flagellates
Trypanosoma brucei
Amoeba
Foraminifera
Paramecium
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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).

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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.

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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.

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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.

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Rhizopus stolonifera
Mushroom - Basidiomycota
Deuteromycota Fruit moulds - Pennicillium
Ascomycota - Morels
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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.

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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

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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).

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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).

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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 doesnt 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.

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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.

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TRACHEOPHYTES Characteristics

• 1. They are vascular plants having 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.)

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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).

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Diversity and success of the Angiosperms

• 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!

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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.

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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.