Topic 1:
TOPIC 1: CLASSIFICATION
OF LIVING THINGS
Kingdom
Plantae
1. Division Coniferophyta (Conifers)
General and Distinctive Features of the Division Coniferophyta
Division Coniferophyta or the conifers belong to
Kingdom Plantae. These plants are gymnosperms (non-flowering). They are
non-flowering but seed bearing plants. They have vascular tissues. They are
woody plants majority being evergreen trees. Few varieties are shrubs
General and distinctive features of the Division
Coniferophyta
General
characteristics
§ They have secondary growth whose thickening can be
observed in cross section of a stem revealing annual rings. Secondary Growth is
the result of growth Lateral Meristems (Vascular Cambium & Cork Cambium).
§ Most of the members of Coniferophyta live in cool
climates
§ They form evergreen forests. They keep their leaves
year-round.
§ They have a large amount of internodal elongation
which allows them to grow faster than the other higher plants.
§ They are Xeromorphic, a characteristic that help to
protect them from excessive loss of water and therefore adapt survival in
extreme habitats.
§ Most are large trees while a few are shrubs and
other small plants.
§ Most of them have hard barks which protect inner
softwood.
Distinctive
characteristics
§ Conifers are non-flowering but seed producing
plants.
§ They have seeds born in cones shaped structures
rather than in fruits.
§ They are gymnosperms which mean naked-seed plants
because they produce seeds in cones rather than inside an embryo.
§ The leaves are needle-shaped and have a thick
cuticle for protection and to decrease water loss.
The
Structure of Pinus
Describe
the structure of pinus
Pines are evergreen, coniferous resinous trees
growing 3-80 m tall. The bark of most pines is thick and scaly. They have
needle like leaves.
Pines are among the most well- known coniferous
trees in the world. They thrive in temperate mountainous regions, but can also
survive in tropical spots in the northern hemisphere. Pines live relatively
long time than other coniferous plants. They may live between 100 and 1,000
years
§ The Stem:The bark of most pines is thick and
scaly, but some species have thin, flaking bark. The branches are produced in
regular whorls appearing like a ring of branches arising from the same point.
§ Leaves:A cross-section of pine stem has
several concentric rings with distinct borders between each ring. The center of
the stem is called pith. These rings are called annual rings because they grow
seasonally and they help a plant to undergo secondary thickening. Generally
adult pines have needle-shaped leaves which are green and photosynthetic. The
leaves are in bundles or clusters. The leaves (cotyledons) on seedlings are
borne in a whorl of 4–24. Juvenile leaves, which follow immediately after
seedlings, have single, green leaves arranged spirally on the shoot. They also
have non- photosynthetic scale leaves, similar to bud scales. They are arranged
spirally like the juvenile leaves.
§ Cones:A cone is an organ of pines that
contains the reproductive structures. The woody cone is the female cone, which
produces seeds. The male cones, which produce pollen, are usually herbaceous
and much less conspicuous. Explain the advantages and disadvantages of the
Division Coniferophyta The advantages and disadvantages of the Division
Coniferophyta
The
Advantages and Disadvantages of the Division Coniferophyta
Explain
the advantages and disadvantages of the division coniferophyta
Advantages of Conifers
i. Conifers are very important for our economy because
of their softwood, which is used for paper and timber, as well as cedar which
many people use for their homes because of its beauty and resistance to
insects. They have a large economic use as softwood in furniture. In temperate
and tropical regions, they are fast-growing softwoods that will allow
harvesting in close succession.
ii. Decoration and ceremony Many pine species make
attractive ornamentals. They are planted in parks and larger gardens. Some
varieties are suitable for smaller spaces. Pines are also commercially grown
and harvested for Christmas trees.
iii. As medicine, Pines and cypress are rich in vitamin;
their branches cones and oils can be extracted and used as nutrient
supplements.
iv. Due to its soft texture conifers are widely used to
manufacture Play wood.
v. As other higher plants conifers are source of heat
energy, used as firewood and charcoal.
vi. Thick forests of conifers form green belts that
modify the climate.
vii. Conifers form a large arena for Biological research
Ecological studies.
viii. Food uses: Some species have large seeds, called
pine nuts that are harvested and sold for cooking and baking. The soft, moist,
white inner bark (cambium) found clinging to the woody outer bark is edible and
very high in vitamins A and C. It can be eaten raw in slices as a snack or
dried and ground up into a powder for use as bread flour. Also White Pines are
rich in Vitamin A and C; flour can be made from the Pine tree's inner bark. By
chewing bark of pine you can eliminate bad breath. Pines can reduce the pain of
skin infections by applying warm pine sap.
2. Division Angiospermophyta (Flowering Plants)
General
and Distinctive Features of the Division Angiospermophyta
Explain general and distinctive features of the
division angiospermophyta
Angiosperms are flowering plants under kingdom
Plantae and division Angiospermophyta. This group of plants is sometimes called
Magnoliophyta. Angiosperms are the most abundant land plants. Like gymnosperms,
angiosperms are seed-producing plants but they are distinguished from
gymnosperms by their characteristic of producing flowers. These plants produce
fruits that contain seeds instead of cones like it is in gymnosperms. The term
angiosperm means a plant that produces seeds within fruits.
Angiosperms life cycle:The
ovary has ovules that contain mega-sporocyte. Mega-sporophyte has four haploid
megaspores; three megaspores disintegrate and the remaining one divides by
mitotic divisions to produce eight nuclei in an embryo sac. The three nuclei
are organized into the egg whereby one cell is the egg cell; the two others are
egg helpers. Although these three cells look are similar, only the egg cell
continues to develop to an embryo sac. The embryo sac at this stage is the
female gametophyte or mega-gametophyte.
Pollination and fertilization:The
pollen from the anther is transported to the stigma of a flower. In the stigma
pollen tube emerges. The mature male gametophyte therefore is a germinated
pollen grain, pollen tube and three sperm nuclei. The pollen tube grows
downward toward the ovary through the style and penetrates the embryo sac.
After discharging its contents one of the sperm nuclei fuses with the egg
nucleus and form a zygote, the other sperm fuses with the polar cell of the
ovary, forming the endosperm nucleus. This is what is known as double
fertilization. Fertilization in angiosperms begins very soon after pollination.
Note: In
gymnosperms, fertilization can occur up to a year after pollination.
Double fertilization:Double
fertilization is a distinctive characteristic of the angiosperms and results in
a polyploid endosperm tissue. In double fertilization each ovule receives a
pollen tube that delivers two sperm cells to the embryo sac. One sperm
fertilizes the egg cell to form the diploid zygote, while the other sperm
fertilizes the central polar cell to form triploid endosperm. After double
fertilization, the ovule develops into a seed and the ovary into a fruit.
General features of angiosperms
They bear flowers which are reproductive
structures. Fertilization takes place between male and female flower by
pollination that includes insect pollination, wind pollination and animal
pollination.
§ Angiosperms have underground root as well as aerial
shoot system.
§ Angiosperms have very well-developed conducting
tissues. These tissues include the xylem and the phloem arranged in form of
vascular bundles.
§ They have root that helps absorption of water and
minerals from the soil.
§ Most of them have leaves that carry out
photosynthesis, so they are autotrophs.
§ They have alternation of generation, Sporophyte
generation alternate with gametophyte generation. The sporophyte is the
dominant, diploid stage and is the more visible form of the plant, with the
leaves, stems, roots, and flowers. Gametophyte generation is reduced and it is
found within the ovary and anther.
Distinctive features of angiosperms
§ The most obvious distinguishing feature of
angiosperms is the possession of reproductive structures called flowers.
§ They bear seeds enclosed in a carpel (the fruit).
The seeds are the fertilized ovules.
§ They have endosperm produced after fertilization
and before the zygote undergo its first division. Endosperm has nourishing
function, it nourishes the embryo.
§ They have double fertilization whereby each ovule
receives a pollen tube that delivers two sperm cells to the embryo sac. One
sperm fertilizes the egg cell to form the diploid zygote, while the other sperm
fertilizes the central polar cell to form triploid endosperm.
§ Their haploid gametophyte is confined inside the
ovary (female) or anther (male) of the flower, unlike the free- living
gametophytes of most other plants.
§ They have conducting tissues phloem and xylem.
Unlike gymnosperms which have xylem tracheid angiosperms has xylem vessels.
The
Classes of the Division Angiospermophyta and their Distinctive Features
Outline the classes of the division
angiospermophyta and their distinctive features
Division Angiosperms is divided into two classes
which are Monocotyledonae and Dicotyledonae. These two classes are distinguished
from each other by their morphology and anatomy.
Features of Class Monocotyledonae
§ Monocots have one cotyledon (or one seed leaf)
§ Monocots have broad leaves with parallel venation.
§ Monocots have fibrous root systems.
§ The floral parts in monocots occur in threes, or
multiple of three. PMonocots lack cambium secondary growth.
§ Monocots have scattered vascular bundles in their
stems.Typical example of monocot is a maize plant.
Features of Class Dicotyledonae
§ Dicots have two cotyledons (or two seed leaves).
§ Dicots have net venation.
§ Dicots have tap root system
§ Dicots floral parts occur in fours and fives and
multiple of four or five.
§ Dicots have cambium secondary growth.
§ Dicots have vascular bundles arranged into a ring.
A Typical example of dicot is a bean plant.
The
Structure of Representative Plants Under Each Class (Monocotyledonae and
Dicotyledonae)
Describe the structure of representative plants
under each class (Monocotyledonae and Dicotyledonae)
Structure ofMonocotyledonae and Dicotyledonae
plants
Advantages
and Disadvantages of Division Angiospermophyta
Explain advantages and disadvantages of division
dngiospermophyta
Advantages of Angiosperms
§ Agriculture. Agriculture depends on
angiosperms. Angiosperms provide human food. Example; plants belonging to grass
family (grains), are the most important food stocks. They include rice, maize,
wheat, barley, millet, sugar cane and sorghum. Legume provides beans, several
varieties of nuts and soy. Also of potatoes, tomatoes, and peppers, pumpkins,
melons and varieties of vegetables to include cabbage and lettuce. Many fruits
oranges, lemons and grapefruits are angiosperms.
§ Livestock. Plants belonging to grass
family are the world number one feeds of livestock. Many types of grassland in
Africa are either grazed by cattle or wild animals. Also almost all feeds
consumed by human are also used by domestic animals as food.
§ Wood. Angiosperms provide different
varieties of wood for furniture, paper and building materials. Carpentry and
masonry depends largely on angiosperms for both soft and hard wood.
§ Textile. Different varieties of fibers
including cotton, flax, and hemp are important raw materials for textile
industry. Cotton is the word first class material for clothes.
§ Medicine. Many organic drugs are coming
from angiosperm herbs. They are either industrial made or can be utilized in
its raw form. Today it is believed that herbs form the best medicine when used
in their fresh form than when industrial made.
§ Floriculture. Flowers
from angiosperms have great social significance as they are used in different
kinds of ceremony. Roses for instance are the most sold flowers and they are
highly purchased and used in wedding and burial ceremonies.
§ Forestry. Forestry is the field of study
whose base depends on both angiosperms and gymnosperms. Many forests form green
belts that habit different varieties of plants.
§ Ecology. Angiosperms provide a wide
range of habitats for different species of organisms. They also serve as
primary producers of energy.
§ Climate. Angiosperms are used to modify
climate. Green belts are established in order to absorb carbon and reduce
global warming.
§ Tourism. Many sites of tourism are
plants oriented. Ecotourism for instance depends largely on different plant
species that host different kinds of land animals.
Disadvantages of Angiosperms
§ Toxins. Some plants are poisonous when
eaten by human and other animals. They cause death to human and other living
organisms. Some cassava varieties are a good example. They have cyanide acid
that inhibits cellular respiration.
§ Drugs. Some angiosperm varieties are
drugs that can be abused when taken. Examples are marijuana, cocaine, tobacco
and some caffeine varieties.