Encyclopedia of popular science knowledge: "Time Knowledge"

Chapter 5 The masterpiece of nature - the biological clock (1)
Fantastic Coral Fossils and Nautilus

Nature has a wonderful clock - the geological clock.What are these?It turns out that corals living in shallow seas have this wonderful clock.

地质学家在研究海洋化石时发现，不同地质年代的珊瑚化石上的条纹不同：石炭纪（距今3亿年前）的地层珊瑚化石一年有385条生长纹；泥盆纪（距今3.5亿年前）的地层珊瑚化石一年有390条生长纹；志留纪（距今4.1亿年前）的地层珊瑚化石有398条细纹，中间夹杂了13个生长带。

How did the traces of these fossils come from?After careful study, scientists believe that those coral polyps living in the crystal clear blue and warm sea water, bathed in sunlight, experienced the changes of day and night and seasons, faithfully recording their own geological history process for hundreds of millions of years.

It turns out that the amount of calcium carbonate secreted by the outer cells of the coral is related to the intensity of sunlight. It secretes more during the day and less at night, so many ring-shaped fine lines are left on the surface of the coral, called growth lines. .With every passing day, a fine line is left behind.

Interestingly, modern corals still have traces of "calendar" and "calendar"!Every 28 growth lines in modern corals, there is a thin and shrinking strip called a growth band, which is similar to the number of days in a month in the modern lunar calendar.In modern corals, about every 360 circles of growth lines, there is an obvious ring, which is composed of many thick and wide growth lines, called growth rings, and the number of days in the same year is similar.Why is this? The "monthly calendar" is because corals have a reproductive climax once a month, and their ability to secrete calcium carbonate decreases, and the rings become thinner and shrink.

The "calendar" is because the life of corals is affected by the seasons. In summer, the water temperature is high and the growth is fast; in winter, the water temperature is low and the growth is slow, so different concave and convex rings are left.

According to the traces of coral fossils, scientists speculate that 5 million years ago, there were about 420 days in a year, and 4 million years ago, there were about 390 days in a year, 30.5 days in a month, and about 21.5 hours a day.From this, a conclusion can be drawn: the closer to modern times, the slower the rotation speed of the earth, the fewer days in a month, and the longer the time of each day and night.

The earth is 46 billion years old, and it has gone through a long time.Coral fossils have become a "witness" in the evolutionary history of the earth, so they are called the "clock" of the earth.Coral fossils are also the "pioneers" of geologists looking for mines, because coral formations of different ages and looks are often treasure houses of petroleum, coal and bauxite.

In nature, in addition to the "clock" of the earth - coral, there is also the wonderful "clock" of the moon - nautilus.

The nautilus looks like a snail, but it is closely related to squid and octopus.The nautilus flourished during the Silurian period of geological history, and began to decline in the Devonian period. In the Triassic period, the straight-shelled nautilus became extinct.And the curly nautilus is rare and almost forgotten.

However, biologists have discovered that there is one genus of nautilus left, a total of three species, which are rare and extremely precious, and are rare "living fossils".

The nautilus lives in the Indian Ocean and the Philippine waters. Its shell is rolled, with a diameter of 20-30 cm.It often crawls on the coral shallow seabed, and occasionally swims, with a posture similar to that of a squid.When strong winds strike, the nautilus floats to the surface of the sea and feeds on small fish, shrimps, and crabs.

There are many short tentacles around the front edge of the head of the nautilus, which are used for predation and action. When the nautilus is looking for food, it stretches out the tentacles, spreads them around, wraps up the prey, and then swallows it.When resting, the tentacles are retracted into the shell, leaving only 1 or 2 tentacles outside to guard. Sometimes if it needs to move quickly, it will spray water like a squid, using the reaction force to propel the body forward.

The shell of the nautilus is divided into many "chambers" by the diaphragm. The outermost chamber is the largest and is the place where the nautilus lives, called the "living room".The other small chambers at the back are smaller and can store air, called "air chambers".There is a small hole in the center of each diaphragm, which is connected into a small tube and connected with the outermost flesh.As the nautilus grows, the number of cells increases.Nautilus relies on this "air chamber" to be able to sink and float freely when floating in the sea.

When scientists study living nautiluses, they find that there are clear rings on the walls of the nautilus' cells, which are its growth lines.There are 30 growth lines on each wall.

The strange thing is that the number of growth lines of nautilus fossils in the same geological age is the same, but that of nautilus fossils in different geological ages is different.For example, the nautilus fossil about 7000 million years ago had 22 growth lines in the cavity; the nautilus fossil about 3.2 million years ago had only 15 growth lines in the cavity.This shows that the growth lines of nautilus are getting fewer and fewer from modern times to ancient times.What's going on here?
According to the calculations of biologists and astronomers: 3.2 million years ago, when the moon was closer to the earth, it took 15 days for the moon to go around the earth, and Nautilus left 15 growth lines every month; 7000 million years ago, the moon was far away from the earth at that time, and it took 22 days to circle the earth, and the nautilus left 22 growth lines every month; now the moon is farther away from the earth, and it takes about 30 days for the moon to orbit the earth. The Nautilus produces 30 growth lines every month, exactly recording the number of days the moon orbits the earth.

The Nautilus lives in the ocean, silently recording the changes of the moon over hundreds of millions of years.It can be said to be a wonderful "astronomer".

Biology's "tide clock"

Tides are a rhythm of nature, the result of the attraction of ocean water to the moon and sun.Many animals in the ocean also have obvious tidal rhythms in activities such as foraging and reproduction, and there is a "tidal clock" in their bodies that dominates.

Small life on the beach, such as clams, mussels and oysters, open their shells at high tide to catch food and close their shells tightly at low tide.

Negreworms often hide in the sand or in the crevices of corals. They seem to be very comfortable, but they are often swallowed by small fish and shrimps.Negreworms kill razor clams, oysters, and various shellfish.

The clamworm body is slender and flat, about 10 cm long, grayish yellow or light red.Consists of many body segments, each with a warty foot on both sides, with setae, suitable for crawling and swimming.During the reproductive season, when the moon is full, the male and female clamworms gather together and float to the surface of the sea, using the sea surface as a "delivery bed", and the moon "deliveries".

Every few days after the full moon, the tails of mature male and female clam worms are full of eggs and sperm, and clam worms divide themselves into two on the seabed—the tail and the mother.The mother stays among the coral reefs, and the tail floats to the surface of the water to lay eggs and ejaculate at sea.Under the transmission of the waves, the tail part dies after completing the reproduction task of life; the other half of the mother body slowly grows reproductive organs in the coral, and reproduces again in the second year.Crowds of fertilized eggs float with the current and slowly hatch into small clam worms.

The conditions when the clam worms lay eggs are mostly similar, but the date of laying eggs is earlier or later in different places.The clamworms of the Malay Archipelago lay eggs between March and April, those of the Gilbert Islands lay eggs between June and July, and those of the Samoa Islands lay eggs between October and November.But the time is always a few days after the full moon, in the evening when the tide is highest.

The wonderful rhythm of the clamworm forms a natural spectacle: the sea is full of fertilized eggs of the clamworm, and even the color of the sea water has become milky white.

There is a mysterious little crab living on the sands of many beaches along the coast of our country and the Atlantic Ocean in the eastern United States. Their habit is related to the tide, so it is called "tide".After the tide ebbs, the fiddler crabs crawl out of the sand and crawl proudly in the sun. Ten minutes before the tide rises, the fiddler crabs always hide safely in their caves.

Scientists believe that there is a mysterious "biological clock" in the fiddler crab to adjust the time. It can change the color according to the sunlight, and can also command the time of foraging or rest according to the rise and fall of the moon and the ebb and flow of the tide.

The silver fish is slender and transparent, shining silver-white light in the bright sunlight.

The common ones in our country are the noodle salmon and the new whitebait in Taihu Lake.

A small whitebait off the coast of California, USA, with a slender body, silvery white, and small eyes like black dots.From March to August every year, it is the spawning and breeding period for small whitebait.The waves rushed them to the beach, and the female anemones kept turning left and right, drilling their tails into the sand to lay eggs.The male rushes to fertilize the eggs, then waits two weeks before another wave comes in and carries the hatchlings back to the Pacific Ocean.This kind of mating action of catching the tide plays a role in protecting the offspring, so that the fish eggs can be hatched smoothly in the sand, and the small whitebait can return to the sea on schedule.

On the Pacific coast of the United States, there is a big tide every year after the full moon in May, and the waves bring groups of perch to the beach.When the waves come at the highest tide, they rush to the beach in large groups. The female bass lays their eggs in the sand, and the male bass rushes to fertilize the eggs.Fish eggs are laid on the sandy beach at the high tide line, which is good for hatching.

There is a bird called damselfish heron, which lives 50 kilometers away from the sea. It flies to the sea every day, and the time is always delayed by 50 minutes from the previous day. It is very regular, which happens to be the same time as the daily tide delay. They are the first eaters on the beach after the tide goes out.

Sunflowers always bloom towards the sun
The golden sunflowers often face the sun, and thousands of small flowers bloom facing the sun.In the morning, when the sun rises, it greets it with a smile; in the afternoon, when the sun hangs high above its head, it faces its back; in the evening, when the sun sets, it turns its head and stares, chasing the sun every day.No wonder people changed their names to "Sunflower", "Sunflower", "Zannichilian", "Sungrass" and so on according to its habits.

Sunflower is an annual herb of the Asteraceae family.It has more than 1000 small flowers on its flower head.

"Flare disc" is many tubular florets that are growing.Each small flower forms a fruit, neatly arranged.There is a circle of yellow tongue-shaped flowers on the edge of the flower disc, which is not fruity.There is also a circle of involucre outside the flower disc, which is formed by the superimposition of many green leaflets, which plays a role in protecting the flower buds.

The blossoming sunflowers are facing the sun, why is this?In long-term research, scientists have found a kind of "plant auxin" in plant stems.This kind of little thing is very interesting. Wherever the sun shines, it will slip away from there, as if playing hide-and-seek with the sun.In the morning, the flower disc of the sunflower faces east, and the sun rises from the east, and the auxin slips from the sunny side to the backlit west side, stimulating the cells there to multiply rapidly, making the backlit side grow faster than the bright side, so the whole The disk is curved towards the sun.As the sun moves in the sky, the auxin in the stem is also constantly moving against the sunlight. Everywhere it goes, it stimulates the cells to grow faster, so that the flower disc will unswervingly rotate with the sun.

Another explanation is that under the sunlight, the electric polarization of the cells occurs in the stem, the sunny side gets negative charges, and the back side generates positive charges.The negatively charged auxin tends to the positively charged dorsal cells, making the backlit side grow faster, bend toward the light, and rotate with the sun.

Sunflower movement toward the sun is a complicated process. During the day, it turns from east to west with the sun, and in the evening, it quietly turns from west to east. By midnight, the sunflower has turned to the east.

Sunflower has a strong ability to adapt to the living environment. It is resistant to hydrochloric acid, drought and waterlogging, and heat and cold. It does not choose the land. It can grow in any open land, embankment corners and other crops where the growth of other crops is not good.In recent years, it has been found that it can improve air pollution and has a particularly good effect.

It can absorb a large amount of nitrogen oxides, which is of great benefit to the protection of the environment.

flowers bloom and fade sometimes

The growth of plants is closely related to the natural environment.Different factors such as light, temperature, water, and humidity make plants form a periodic life law in the process of long-term natural selection and adaptation.

There are always flowers blooming, and the flowering of plants varies with the change of day and night and seasons. Some of them bloom in full bloom during the day, and some bloom in full bloom under the moon; some bloom in spring, and some bloom in autumn.

Flowers are particularly sensitive to sunlight. The same flower blooms earlier in the south and later in the north due to the difference in light and temperature.Most of the flowers open during the day, but there are differences in the morning and evening.

Some flowers are very delicate and are afraid of being burned by the sun. They bloom early and close quickly. Hops and morning glory bloom before dawn, because the air is humid and the light is soft in the morning. , the sun became stronger and the air drier, they rolled up so as not to burn.

Scutellaria barbata, also known as sunflower, loves the sun. It blooms at 10 o'clock in the morning. The stronger the light, the more beautiful the flowers bloom, and it closes after noon.Although it blooms in cloudy days, it closes slowly, and it becomes dejected.

Dandelion likes to chase the sunshine. It blooms at sunrise and closes every day. However, on cloudy days, it closes its petals tightly, like a yellow feather brush.The sensitivity of gentian in the Alps to sunlight is even more peculiar: when the sun is covered by clouds, it closes quickly; as soon as the sun breaks out of the clouds, it blooms again.

When the flowers bloom naturally, it is also related to the pollination and reproduction of the flowers.Generally, there is no morning or evening for anemophilous flowers to bloom, but insect-pollinated flowers are different. Bees gather flowers early, and bee-pollinated flowers bloom early; butterflies come out later, and butterfly-pollinated flowers bloom later; noctuids come out to pollinate at night Yes, a few flowers open just after evening.

Mirabilis bloomed around 5 pm, and the flowers closed at dawn the next day, as if they were afraid of seeing the sun.The moonlight flower of Convolvulaceae blooms around 8 o'clock at night, and does not close until the next morning. The flowers are white and fragrant. It is a veritable flower that blooms with a smile under the moonlight.As night falls, the tuberose is white like jade, exhaling a burst of fragrance, and the fragrance of the flower gradually becomes stronger, so it is called "Moon Night Fragrance", "Evening Fragrance", and "Night Love Fragrance".The yellow flowers of the night grass of the willow-leaf family do not open their smiling faces until night, which just shows its life rhythm of closing day and blooming at night.Vegetable gourds are also called night blossoms, and they get their name because they bloom at night.

The most interesting thing is to count the flowers of peanuts.Its flowering time is long or short, which varies with the length of day and night. In July, peanuts bloom at 7 o'clock in the morning and close at 6 o'clock in the afternoon; in September, they bloom at 6 o'clock in the morning and close at 9 pm.On rainy days, the flowering time is even shorter.

In the morning, when the sun rises, the petals of the water lily gradually bloom, and the smiling faces greet them, and when the sun goes down, the flowers close.Water lilies close at night because the temperature at night is lower than that during the day, which can keep the delicate stamens from freezing to death.

Crocus blooms in early spring, and it opens and closes several times a day.It turns out that crocuses are sensitive to temperature changes.When the temperature rises, the inner side of the flower grows faster and blooms. When the temperature drops, the outer side of the flower grows faster than the inner side and closes.

The biological clock of plants is relatively correct, but it is also easily adjusted by the external environment.

If the day and night rules of plants are reversed, and the lights are illuminated at night and placed in a dark place during the day, the plants will adjust the "biological clock" in the body according to the new light cycle, and follow a new set of life rhythms again.

The "clock" in the body of the cockroach

Cockroaches are pests that often haunt family kitchens, even restaurants and ships at night, making some food dirty.As soon as the light came on, it slipped away quickly.

Cockroaches are sensitive, its tentacles are the most sensitive parts, and the nerve endings on the leg joints are quick to perceive the slight sound and light footsteps.

Scientists have discovered under a microscope that the nervous system of the cockroach has 14 pairs of giant interneuron nerve cells, and each tail has about 220 hairs, which can detect the weak tremors of the ground and air and respond immediately.When a person walks, the ground and the air vibrate weakly, which will deform the beard and hair, and the sensory nerve at the root sends a signal to the neuron, which is transmitted to the leg, contracts the muscle, and escapes at an alarming speed.

Scientists have conducted many experiments on cockroaches, shutting the cockroach in a secret room, automatic instruments to control the internal temperature, humidity and air pressure, isolating all external sounds, and tracking its actions with infrared rays.A week later, I learned the behavioral pattern of cockroaches, the cycle is 23:53.This is somewhat similar to the period of the earth's rotation!Strange, in the dark secret room, how does it know that the night of the outside world alternates?

Scientists conducted another experiment, artificially creating a new environment, reversing the circadian rhythm of nature, allowing cockroaches to live in it, and tracking its activities with electronic eyes.In this way, day becomes night, and night becomes day.After a week, the cockroaches adjusted their original rhythm of life and moved in the artificial dark night instead.

Scientists believe that there is a wonderful "clock" on the cockroach, which indicates the activity and rest of the cockroach.Where is this "biological clock" hidden?There is a ganglion in the pharynx of the cockroach, and there are a group of neurosecretory cells on its side and ventral surface, which secrete and regulate hormones and issue "commands" for action.

People once took this tissue from one cockroach and transplanted it to another cockroach. This strange clock still oscillates regularly. When this tissue is cooled to 0°C, it works. It stops, the humidity builds up, and the clock starts ticking again.

However, after the nerve tissue of the cockroach was removed and "stopped" for a period of time, its activity became regular again.What is the reason?Scientists have discovered that in addition to this "clock", cockroaches also have a more important "mother clock" that is swinging time.This "mother clock" is the synapse at the end of the nerve fiber axon and other nerve connections, and the hormones it secretes control the general "biological clock" (secondary clock).

Scientists believe that the "child clock" indicates the cockroach's daily activities, while the "mother clock" comes out to play its role when the "child clock" deviates or when the "child clock" stops.

Autumn to Spring Talking to Migratory Birds
(End of this chapter)