Reading (part I): From chick to chicken + reading comprehension
Reading
A bird`s egg is rather like a spaceship. Inside there is a living thing - a chick- which has to survive in the hostile environment outside its mother`s body. The shell of its "space capsule" provides protection, and inside is all the food and water that the living inhabitant requires. The egg is also equipped to store the waste products of its occupant in a special sac. Oxygen can travel in from the air outside, but the tiny pores through which it passes are too small to let much water out. When the chick has reached the right stage of development, it breaks open the shell and struggles free into the outside world.
From chick to chicken
When it is first formed, a hen`s egg is a single cell. After fertilization, the original single cell divides into many smaller cells inside an egg. When it is laid, the hen sits on the egg, or "incubates" it. Unless it is kept at a constantly warm temperature in this way, the chick will not develop properly. About three weeks after laying, the chick inside the egg is fully developed and is ready to hatch. At first, the chick obtains oxygen from its blood vessels, chich come into contact with air flowing through the shell. But as the egg is incubated, it loses some water, and an airspace develops at its blunt end between the shell lining`s two membranes. The chick pushes its beak into airspace a few days before it hatches.
1. When the egg`s air supply is used up, another oxygen sourse is needed. The chick pokes a hole in the eggshell and breathes fresh air from outside. When it is ready to emerge, the chick pecks out a circle of holes in the blunt end of the egg. It has a special chalky tip to its beak, known as an egg tooth, to enable it to crack through the hard shell.
2. Using its feet, the chick forces away the blunt end of the eggshell and completes the hatching process. A young chicken is " precocial" - it can run about and feed itself within a few hour of hatching. The young of "altrical" birds, such as house sparrows, are helpless at hatching. They are reared in nests by their parents.
3. Young chicks have well developed heads and feet, but small, stubby wings. They connot fly, but they can run quickly to escape danger. They can find all their own food because when they hatch, they have a strog instinct to peck at anything that might be edible.
4. Young chickens learn the sound of their mother`s call while they are still in the egg, and they follow her as soon as they can walk. They quickly learn to recognize her by sight as well, a process known as imprinting. If eggs are incubated artifically, the chicks well imprint on the first moving being they see when emerge from the egg.
Exercises
1. If necessary, read the text again. Then comment on the following:
a/ the author compares an egg to a spaceship
b/ an egg must be kept at a constantly warm temperature (give reasons)
c/ what is taking place inside an egg a few days before hatching?
d/ the process of hatching
e/ an egg tooth
f/ are chicken and "altricial" birds born with the same abilities to survive shortly after hatching?
2. Here are the answers to some questions. Write down the questions.
a/ __________________________________________?
It is stores in a special sac.
b/ __________________________________________?
No, it isn`t. It is permeable to gases.
c/ _________________________________________?
After fertilization.
d/ __________________________________________?
It assures proper development of a chick inside an egg.
e/ _________________________________________?
Through the shell.
f/ ____________________________________________?
Yes, it can. A young chicken is "precocial"
g/ __________________________________________?
By sight.
3. The following are definitions of words from the article you have just read. What are the words?
a/ hard outer case of an animal, fruit, etc.
b/ unit-mass of living matter; a small unit of protoplasm: all plants nad animals are made up of one or more of them
c/ to make fruitful by introducing the male germ cell
d/ to take (air) into lungs and let it out again; inhale and exhale
e/ the structure or place where a bird lays its eggs and shelters its youing