BIOLOGY HOLIDAY ASSIGNMENT.
1. What is growth?
- Growth is the permanent increase in amount of living
matter(protoplasm) in organisms. It is always accompanied by
increase in size and mass. It involves assimilation, cell division
and cell enlargement. Development is due to differentiation of
cells.
2. Describe the two types of growth that occur in plants.
- Primary growth: this occurs at the menstems only. There are
types of menstems; the epical menstem and lateral
menstem(cambia) it results in the increase in height of shoot
and length of root.
- Secondary growth: this growth arises from the activities of the
cambium(lateral menstem) it leads to the increase in the
diameter of stems and roots of woody plants. Secondary
growth(thickening) occurs as a result of new xylem and phloem
respectively.
3. With the aid of diagrams describe the life cycle of
i)
House fly.
-
The female housefly deposits her eggs in the crevices and corners of the
same kinds of decaying organic matter adults feed on. Within a day, the
first larvae begin to emerge from the eggs. Also known as maggots,
these worm-like creatures are little more than fleshy, sectionless tubes
with hooked mouth parts used for feeding. The maggots grow rapidly.
In less than two days they've doubled in size and therefore must molt.
Molting is a process common to many invertebrates through which a
growing insect sheds its former exoskeleton and grows a new one. A
maggot will molt twice more, emerging larger and more developed
each time. Following its third molt, larvae will burrow deep into the
substance they've been feeding on. Their skins will darken and harden
as they enter the pupa stage. Inside this protective shell, the larva will
fully develop the body segments and appendages of an adult housefly.
The only visible addition to the emerging housefly is a swollen bump on
the fly's head, used to break through the shell. Since the housefly
doesn't have teeth or jaws to chew its way out, it uses this fluid-filled
pouch to break through the pupae shell. Once fully emerged, the bump
deflates back into the fly's head. A new adult housefly has, at most,
three months to reproduce before it dies. With so many predators, a
housefly's average lifespan is even shorter: 21 days. Luckily for the
housefly, the phrase "breeding like flies" isn't just a figure of speech.
Each female can lay up to 900 eggs during her brief life.
ii) Mosquito.
- The mosquito is a biological vector for many diseases like
yellow fever, malaria and elephantiasis. One stage of the cycle
of the parasite takes place in the mosquito. The mosquito only
lays eggs in stagnant water. The eggs hatch to larvae. The
larvae hatch to pupae that also breath by use of spiracles in
water. The adult take one week to emerge and the female
anopheles looks for human beings and other primates like
monkeys for a blood meal to make sure that their eggs develop
properly before fertilization. The mosquito usually bit at night
and hid in dark places either in the house or bush. When a
mosquito bites a person infected with malaria the pathogens
go to the mosquito’s system. when the mosquito bites another
person, it releases saliva to stop blood from clotting, parasites
in the saliva pass on the healing person and find their way into
the blood efficiently spreading the disease.