Animal reproduction and development

Most animals lay eggs or eggs. Animals give birth to cubs and feed them with milk. As they develop, the offspring turns into adult animals. Many parent animals care for their offspring.

Reproduction and development of insects
The nettle butterfly lays eggs on nettles. The eggs hatch into larvae. Butterfly larvae are called caterpillars. They look nothing like adult butterflies. The caterpillars feed on nettle leaves, grow quickly, and then turn into motionless pupae. A little time will pass, and an adult butterfly will emerge from each pupa.
Not all insects can have pupae. For example, grasshoppers do not have pupae. Their larvae are very similar to adult grasshoppers, only they are very small and do not have wings. Growing up, each larva sheds its skin several times. When this happens for the last time, an adult insect emerges from the skin - large and with wings.

Reproduction and development of fish, amphibians and reptiles
In spring, female fish spawn eggs into the water. From the eggs emerge fry that are similar to adult fish, only very small. The fry feed, grow and gradually become adult animals.
In spring, in the pond, river, lake, the loud voices of frogs and toads are heard - real concerts! At this time, female frogs and toads lay eggs in the water. After a few days, the eggs hatch into tadpoles that look more like small fish than adult amphibians. Tadpoles live in water, feed, grow and gradually develop into adult frogs or toads.
Female lizards, snakes, turtles, and crocodiles lay eggs. The eggs hatch into small lizards, snakes, turtles, and crocodiles. They grow and gradually turn into adult animals.

Bird reproduction and development
Almost all birds build nests in the spring. Birds lay eggs in nests and incubate them - warming them with their warmth. Chicks emerge from the eggs. Some birds are already covered with down and very mobile, while others are helpless and naked. They grow quickly and need a lot of food. At the end of spring - beginning of summer, the chicks of many birds leave their nests.

Reproduction and development of animals
Animals, or mammals, give birth to young and feed them with milk.
Most mammals give birth to their young in the spring. For a fox they live in a hole, for a squirrel - in a hollow or in a nest in a tree. At the beaver's house - hut.
Most animals take care of their offspring: adults protect the cubs, and over time teach them to obtain food on their own.

What bird is the riddle talking about?

Who is this bird? Never
Doesn't build nests for itself,
Leaves eggs for neighbors
And he doesn’t remember the chicks.
Answer: Cuckoo

In what kind of houses do animals raise their offspring?

Consider the houses of some birds. Think about how they built them. Which bird did not build a house itself? Why?

WoodpeckersThey hollow out a new hollow in a tree trunk or clean and expand an existing one, but it is not large enough. A person will never see a woodpecker's nest on a green tree. These birds choose dead and diseased trees for their nests.
stork nest very large up to 1.5 m in diameter and can weigh up to 250 kg. It is usually found on the roofs of various human structures or on broken tree tops near wetlands. The nest has been used by the stork for more than one year, so it is built conscientiously and is annually repaired and updated. The height of a fresh nest reaches 40-50 cm, and old ones can be up to 1.5 meters high. The oldest nest is known in Germany, in which storks nested for 381 years in a row.
Martin builds his own nest from lumps of damp earth. She finds earth in puddles, rolls them into balls, brings them in her beak to the construction site and firmly attaches them to the wall, gluing them with her own saliva. To make the structure stronger, the barn swallow mixes straws, stems, and horsehair into the soil.
Goldfinch builds nest very densely (cup-shaped) made of thin stalks of moss, lined inside with plant fluff (from the fruits of poplar, willow).
Starling people love it, it destroys many harmful insects, which benefits people. We are accustomed to the fact that starlings live in birdhouses.
Beregovushka- the smallest and most inconspicuously colored of our swallows. One of the birds that make nests in burrows and do not occupy other people’s homes, but dig them themselves. Even if last year’s home is intact, shore swallows still prefer to build a new one.

Class: 3

Presentation for the lesson

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Class: 3.

Lesson objectives:

• Introduce students to the reproductive characteristics of animals of different groups.
• To form an idea of ​​the sequence of development of animals of different groups.
• During the lesson, curiosity and coherent speech develop; the ability to reason, observe, generalize, draw conclusions, and work in pairs.

Equipment:

• Computer.
• Media projector.
• Power point presentation.
• Tables of development of representatives of different groups of animals.

During the classes

I. Report the topic of the lesson.

- We need a new shirt. What are we doing? (We buy a new shirt or sew it ourselves.)

– We need grass on the lawn in front of the house in the country. What are we doing? (We sow seeds, grow them, water them.)

– It’s true that in order to get a new object, a person makes it from other materials. To get a new plant, we grow it: we sow seeds, plant bulbs, bury tubers, take cuttings, etc. (depending on the method of reproduction).

Animals, like all other living things, reproduce. Today we will talk about what features of reproduction and development are characteristic of different groups of animals.

II. Preparation for the perception of new material, repetition of previously studied.

• Let's remember what main groups scientists group animals into. (Insects, fish, birds, reptiles, amphibians, mammals. As well as worms, mollusks, arachnids, crustaceans.)

Slide 2

• What groups can animals be grouped into, taking into account what they eat? (Herbivores, carnivores, omnivores.)

- Give examples.

Slide 3

• What groups can animals be grouped into based on their ability to live and reproduce in captivity? (Wild and domestic animals.)

Slide 4

• And my next question will take us to a new topic. Let's try, remembering the previous material, to answer the question: into what groups can animals be divided, taking into account their methods of reproduction? (Oviparous; animals that spawn in water; viviparous.)

Slide 5

III. Learning new material: Reproduction and development of insects.

Slides 6–14

• Insects have males and females. Thus, insects are dioecious inhabitants of our planet. Like most species of living creatures, male and female insects have differences, which can be expressed, for example, in bright coloring, size - males are most often larger, but there are exceptions.

This, of course, is necessary so that the female and male can find each other. Different insects search in completely different ways. Some sing serenade songs, while others glow like a small flashlight, like fireflies, for example. Some insects emit odors, sometimes fragrant (rutberries smell like lemon leaves), and sometimes not very pleasant to the human nose.

So, the female and the male found each other. The female laid eggs.

I think now it’s time to find out how the future development of the future insect will occur.

I propose to observe a butterfly called admiral.

Having laid an egg on the leaf of a food plant, the female no longer worries about the future fate of her offspring. She does not watch how the larva emerges from the egg (in butterflies it is called a caterpillar). This is a very voracious creature that is not at all like its parents. The caterpillar feeds intensively, grows and molts.

After some time, the next stage of development will begin: the caterpillar will turn into a pupa. This is indeed a motionless pupa, which attaches to the surface of the leaf and waits for the next stage - the appearance of an adult insect.

• So, let's create a diagram of insect development using the admiral butterfly as an example. (Egg, caterpillar, pupa, adult insect.)
• It should be noted here that not all insects follow this development path. Among the representatives of this group of animals there are also those that do not have a pupal stage, and the larva looks like an adult insect. For example, these are grasshoppers and dragonflies.

IV. Learning new material: Reproduction and development of fish.

• To have an idea of ​​the reproduction and development of fish, let's take a closer look at the life of pink salmon. During the mating season, the male pink salmon changes color, its jaws become curved, and a hump grows on its back. The female does not change.

The female spawns eggs into the water, and the male waters them O kami. Each individual egg can develop into a larva. The larva develops into a fry, and the fry develops into an adult fish.

Slides 15–19

V. Learning new material: Practical work in pairs.

• Compare larvae, fry, and adult pink salmon fish. Find similarities and differences.

VI. Learning new material: Reproduction and development of birds.

• Let's, based on our life experience, try to create a chain of bird development. (Egg, chick, adult bird.)

- Well done! And here it is necessary to pay attention to the following features of bird development.

1. All birds breed on land.
2. Most birds build nests.
3. Birds incubate eggs, warming them with body heat.
4. Parents feed the chicks and protect them from enemies.

Slides 20–21

VII. Learning new material: Reproduction and development of mammals.

– We have just concluded that birds are a very interesting group of animals that take care of their offspring. What other group of animals cares for their offspring? (Mammals.)

- Right. Let's draw a conclusion.

1. Mammals give birth to live young.
2. The mother feeds them with milk, cares for them, protects them, teaches them how to get food, and how to defend themselves from enemies.

Slides 22–23

VIII. Lesson summary.

• What is the name of the butterfly larva? (Caterpillar.)
• What develops from a fish larva? (Little one.)
• What are the similarities between the reproduction of birds and insects? (They lay eggs.)
• What are the similarities between the reproduction of birds and mammals? (Take care of the offspring.)

Images used in the presentation are taken from.

Our planet is inhabited by a large number of a wide variety of animals that have adapted to life in different parts of the Earth. As a result of such diversity, the reproduction and development of animals also has many differences and features.

Insects

Insects have males and females, which can differ in size and color. The female lays eggs and no longer cares for her offspring. She does not protect them from other animals, does not watch the larvae emerge from the eggs.

The larvae look completely different from their parents. These are small and incredibly voracious creatures that feed intensely and increase in size.

After some time, a new period of development begins: the larvae turn into motionless pupae, which attach to the plants, waiting in the wings. After the allotted time, a fully formed adult insect emerges from the pupa, ready for a full life.

To leave offspring, the female and male must meet each other. But how to do that? Many insects use various tricks: they sing serenade songs, glow like tiny lanterns, and emit strong odors.

Rice. 1. Mantises.

Fish, amphibians and reptiles

The reproduction and development of fish occurs in stages:

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• In the spring, females lay eggs and the male fertilizes them.
• Each egg develops into a tiny larva.
• Over time, the larva turns into a fry.
• The fry, actively feeding, increases in size and turns into an adult.

Turtles, crocodiles, snakes, lizards lay eggs, from which small cubs are born, which are no different in appearance from their parents, except for size.

In nature, there are two types of reproduction - sexual and asexual reproduction. The first option is used by all animals with a complex body structure: mammals, birds, fish, insects, reptiles and amphibians. The asexual type of reproduction is characteristic of unicellular organisms that form their own kind through cell division.

Rice. 2. Baby turtles.

Birds

In the spring, many birds begin to build nests - this is how they prepare for the appearance of offspring. Birds lay eggs in nests and then hatch them, warming them with body heat.

After a while, baby birds emerge from the eggs - chicks. In some birds they are active and inquisitive, and their bodies are covered with down; in others, the chicks are born naked and completely helpless. But all of them, without exception, at first depend on parental care, since they do not know how to fly or get their own food.

To feed their insatiable babies, birds are forced to search for suitable food from morning to evening. However, such efforts quickly pay off - already at the beginning of summer, the matured chicks of many birds leave their parental nests.

Mammals

Mammals or animals, unlike other animals, give birth to live young and feed them with their milk. Until the kids get stronger and are ready for adult life, parents carefully look after them, protect them from enemies, and teach them how to get their own food. As a rule, all these functions rest on the shoulders of the mother, but there are mammals that raise their offspring together.

While the kids are helpless, they have many enemies. To avoid becoming easy prey, they hide in their home almost all the time. Fox and badger cubs hide in deep holes, squirrel cubs are securely hidden in a nest in a tree or in a hollow, bear cubs' home is a spacious den.

Rice. 3. Fox with cubs.

What have we learned?

When studying the 3rd grade program of the surrounding world, we learned what the features of the development and reproduction of different representatives of the fauna are. Each of them was able to adapt to the conditions in which they live and raise their offspring. Some babies are immediately born as small copies of their parents, while others have to go through a long development path from a tiny egg to an adult animal.

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Lesson summary

around the world

Subject:

Animal development and reproduction

Teacher: Zyuganova Elena Nikolaevna

Subject: “Development and reproduction of animals”

Target: get acquainted with the features of animal development and reproduction

Tasks: create universal learning activities within the lesson

Personal UUD:

Formation of a holistic, socially oriented view of the world in its organic unity and diversity of nature;

In the proposed situations, based on the rules of behavior common to all, make a choice about what action to take;

The ability to determine your attitude to the world.

Regulatory UUD:

Formulate lesson goals independently after preliminary discussion;

Together with the teacher, discover and formulate an educational problem;

Draw up a plan for solving a problem (task) together with the teacher;

Working according to the plan, check your actions with the goal and, if necessary, correct mistakes with the help of the teacher.

Cognitive UUD:

1. General educational universal actions:

Formulating the topic of the lesson;

Search and selection of necessary information (work in groups with the text and illustrations of the textbook, visual aids);

The ability to adequately, consciously and voluntarily construct a speech statement in oral form;

Meaningful reading as understanding the purpose of reading.

2.Universal logical actions:

Analysis of objects in order to highlight significant features;

Synthesis as the composition of a whole from parts;

Selection of bases for comparison;

Summing up concepts, object recognition;

Establishing cause-and-effect relationships, building a logical chain of reasoning and evidence;

Proposing hypotheses.

3. Statement and solution of the problem:

Independent creation of activity algorithms when solving search problems.

Communication UUD:

Ability to listen and engage in dialogue;

Participate in collective discussion of problems;

Integrate into a peer group and build productive interactions and collaborations with peers

Basic methods and technologies for UUD development used within the lesson:

technology of problem-based and dialogic learning

productive reading technology

technology for assessing educational success

group work technology

Equipment: textbook, tables, pictures, presentation.

1. Organizational moment.

2. Checking the data

List the names of the spring months in order. (March April May.)

What changes occur in nature with the arrival of spring.

Spring changes in nature

3. Updating knowledge.

Spring also brings changes to the lives of animals.

Let's remember what main groups scientists group animals into. (Insects, fish, birds, reptiles, amphibians, mammals. As well as worms, mollusks, arachnids, crustaceans.)

Slide 2

What groups can animals be grouped into, taking into account what they eat? (Herbivores, carnivores, omnivores.)

- Give examples.

Slide 3

What groups can animals be grouped into based on their ability to live and reproduce in captivity? (Wild and domestic animals.)

Slide 4

And my next question will take us to a new topic. Let's try, remembering the previous material, to answer the question: into what groups can animals be divided, taking into account their methods of reproduction? (Oviparous; animals that spawn in water; viviparous.)

Slide 5

4. Creating a problematic situation

I see that you are ready to discover new knowledge. Do you think we know everything about a group of animals and their representatives? And write what the cubs of animals are called. Slide 6

The fox has ... (little fox)

The duck has ... (duckling)

The butterfly has ... (caterpillar)

The fish has ... (fry)

The grasshopper has... (larva)

The snake has ... (snake)

(not entirely accurate, if you don’t know, leave a space)

Guys, who was the frog in childhood? And the crocodile? Snake?

Why did you get different answers?

You see, we don’t know everything about animal groups.

Maybe you already guessed what we will study today?

What do you want to learn about in class today?

5. Subject message

Animals, like all other living things, reproduce. Today we will talk about what features of reproduction and development are characteristic of different groups of animals.

Formulate the topic of the lesson? Slide 7

Formulate the objectives of the lesson. Ask questions. Slide 8

1.How do insects reproduce?

2.How do fish reproduce?

3.How do fish, amphibians, and reptiles reproduce?

4.How do birds reproduce?

5.How do animals reproduce?

6. Children's discovery of new knowledge.

1) Group work on the textbook page 73

– Which animals lay eggs? -Insects, reptiles, birds

Which animals spawn? -Fishes, amphibians.

How does the reproduction of animals differ from other animals? -Animals give birth to young

Reproduction and development of mammals: CHILD – ADULT ANIMAL Slide 9

2) Work in groups Slide 10 -14

You will study the development and reproduction of animals in your group using the example of your representative.

1 group

Insects

2nd group

3 group

Amphibians

4 group

Reptiles

5 group

Read the scientific educational text. Highlight the main developmental stages of your animal. And with the help of pictures and words, draw up a diagram of the reproduction and development of the animal. At the end of the work, choose a speaker.

Reproduction and development of insects: Slide 10

Option 1 - compose the development of a butterfly; Option 2 – grasshopper development

EGG – LARVA (CATERPILLAR) – PUPA – ADULT INSECT;

EGG – LARVA – ADULT INSECT

Reproduction and development of fish: Slide 11

CAVIAR  FREE  ADULT FISH

Reproduction and development of amphibians: Slide 12

Caviar - tadpole - frog.

Reproduction and development of reptiles: Slide 13

EGGS – CHILDREN – ADULT ANIMAL

Reproduction and development of birds: Slide 14

EGG – CHICK – ADULT BIRD

7. Consolidation of what has been learned

Blitz survey.Slide 15

What is the name of the butterfly larva? (Caterpillar.)

What develops from a fish larva? (Little one.)

What are the similarities between the reproduction of birds and insects? (They lay eggs.)

What are the similarities between the reproduction of birds and mammals? (Take care of the offspring.)

What conclusion can be drawn about animal reproduction? Slide 16

(Animals give birth to young and feed them with milk. But most other animals lay eggs and caviar. In birds, chicks emerge from eggs, in insects - larvae. In fish, fry emerge from eggs, in frogs and toads - tadpoles. As they develop, they all turn into adults.)

8. Lesson summary. Relaxation.Slide 17

What new did you learn in the lesson?

Now pick it up green cards those guys who understood everything during the lesson, red- if nothing was clear in the lesson at all.

Application

cub bear

Python snake eggs

Eggs chicken chicken

Eggs caterpillar pupa butterfly

Tadpole frog eggs

Crucian carp caviar

Cards for group work.

1 group. Insects

Read the scientific educational text in the textbook on page 78. Highlight the main stages of development of your animal. Using pictures and words, draw up a diagram of the reproduction and development of the animal. At the end of the work, choose a speaker.

2nd group. Fish

Read the scientific educational text in the textbook on page 76. Highlight the main stages of development of your animal. Using pictures and words, draw up a diagram of the reproduction and development of the animal. At the end of the work, choose a speaker.

3rd group.Amphibians.

Read the scientific educational text in the textbook on page 77. Highlight the main stages of development of your animal. Using pictures and words, draw up a diagram of the reproduction and development of the animal. At the end of the work, choose a speaker.

4 group. Reptiles.

Read scientific and educational text see Attachment. Highlight the main stages of development of your animal. Using pictures and words, draw up a diagram of the reproduction and development of the animal. At the end of the work, choose a speaker.

5 group. Birds.

Read the scientific educational text in the textbook on pages 74 -75. Highlight the main stages of development of your animal. Using pictures and words, draw up a diagram of the reproduction and development of the animal. At the end of the work, choose a speaker.

Application.

Turtles- a detachment of reptiles that has existed for 250 million years, living both in water and on land. All modern turtles known to science are oviparous animals. Females lay eggs in a pitcher-shaped hole, which they dig with their hind paws (some in their own living burrows (gophers) or in the nests of crocodiles), wetting the soil with fluid sprayed from the body. Then the hole is filled up and compacted from above with blows of the plastron. The eggs are spherical or elliptical, white, usually covered with a hard calcareous shell. Only sea turtles and some side-necked turtles have eggs that have a soft, leathery shell. The number of eggs laid varies among different species from one to two hundred.

Lizards. Most species of lizards are oviparous, some are ovoviviparous. In this case, the mother animal does not lay eggs or eggs, but carries them inside itself. The cubs leave the egg shell while still in the mother's body and are then born.

Most lizards lay eggs. Typically, eggs have a thin, leathery shell, less often (mainly in geckos) a dense, calcareous shell. The number of eggs varies among different species and can range from 1-2 to several dozen. The female lays eggs during the year one or several times, in a wide variety of, but always secluded places - in holes, cracks, under stones and snags, in tree hollows, etc. Some geckos glue eggs to tree trunks and branches, in places rock outcrops, etc. In most cases, after laying eggs, lizards do not return to them. Only a few of them take care of their offspring. Among our lizards this is the yellow-bellied lizard. Females of this species not only guard the clutch, but also look after it - periodically turning it over and cleaning it of debris.

For some time after the young yellowbells hatch, the females continue to protect them and even give up food.

One of the forms of caring for offspring may include the ability of some lizards to delay the laying of eggs, waiting for the onset of conditions favorable for this. Thus, in the sand lizard, egg laying can be delayed for 20 days. In others, for example, in a viviparous lizard, it continues until hatching.

One of the reasons causing viviparity is cold climate. It is interesting that even lizards of the same species, depending on the altitude above sea level, can either lay eggs or give birth to live young.

Various types of snakes reproduce differently. For example, rattlesnakes, copperheads, and water snakes do not lay eggs, but give birth to live young. Snakes are known that can give birth to up to 75 cubs at a time. Other snakes lay eggs. They usually do this in secluded places, under rocks, under logs or in empty tree stumps. Snake eggs are somewhat different in shape from chicken eggs: they are smaller and longer. Although the eggs of large snakes may not be inferior in size to chicken eggs.

The shell of a snake egg is quite strong and resembles skin. The number of eggs in a clutch varies depending on the type of snake. The python probably lays the most eggs. The Indian python can lay up to 107 eggs at one time.

The eggs are usually aged in the sun or in the heat generated by decaying vegetation. Sometimes snakes guard eggs by coiling around them.

But who takes care of the growing offspring if the number of eggs in a clutch reaches 100? Nobody! All small snakes are able to take care of themselves from the moment they are born.

Due to the extremely high level of their existence and structure, several types of reproduction and postembryonic development have formed, which pass on genes to the offspring and continue to ensure the survival of the species.

The process of reproduction is one of the important properties of organisms and is divided into two ways: asexual and sexual.

The sexual method is used by animals with a complex body structure, such as crustaceans, and, basically, all vertebrates.

Animals have two mechanisms of fertilization: external and internal.

External fertilization

One of them is external fertilization, in which eggs and sperm fuse outside the animal’s body. For example, this method of fertilization is used by fish and amphibians. This type of fertilization is called spawning and occurs in an aquatic environment. Accordingly, sperm need water to swim to the laid eggs, and eggs in turn need water to prevent drying out. Most aquatic invertebrates, most fish, and some amphibians use external fertilization. These animals release large quantities of sperm and eggs because they suffer significant losses of gametes in the water. Therefore, fish simply need to spawn a large amount of eggs. Thus, female perch lay 200-300 thousand eggs, and female cod lay up to 10 million. In addition, courtship behavior in some species leads to the simultaneous release of gametes, which helps provide the egg with sperm.

Gametes, or sex cells, - reproductive cells that have a haploid (single) set of chromosomes and participate in gametic, in particular sexual, reproduction. When two gametes fuse during the sexual process, a zygote is formed, which develops into an individual (or group of individuals) with the hereditary characteristics of both parental organisms that produced the gametes. Wikipedia

Paying attention to goldfish breeding It should be noted that single-sex populations occur here (there are usually no males). The development of eggs of this species occurs after the sperm of a completely different species of fish (carp, goldfish, tench) penetrates them. But in this case, standard fertilization does not occur. In this case, the sperm is only an irritant that awakens the egg to development.

This type of external fertilization, or rather spawning, also includes seahorses. Like no one else, they mate in a bewitchingly romantic way and dance until the female places her eggs in the male’s special pouch. It turns out that the seahorse is a conscious male who becomes pregnant and bears its offspring. After the male gives birth, he leaves his young to develop and fend for themselves.

Internal fertilization

Another example of sexual reproduction is internal fertilization, in which the male injects sperm into the female's reproductive tract, where the eggs are fertilized. This fertilization is an adaptation to life on land because it reduces the loss of gametes that occurs during external fertilization. Sperm are equipped with a fluid (sperm) that provides an aqueous environment inside the male's body. Mating and reproductive readiness are coordinated and controlled by hormones so that sperm and eggs come together at the appropriate time.

After internal fertilization, most and all reptiles lay eggs, which are surrounded by a tough membrane or shell. Their eggs have four membranes: amnion, allantois, yolk sac and chorion. The amnion contains the fluid surrounding the embryo; The allantois stores the embryo's urinary waste and contains blood vessels that bring oxygen to the embryos and take away carbon dioxide. The gall sac holds the stored food, and the chorion surrounds the embryo and other membranes. In birds and reptiles, the embryo matures outside the body and is protected by a membrane.

Basically, everyone (cows, yaks, hippos, rabbits, dogs and many others) use internal fertilization, but there are exceptions - such as and, which lay eggs.

Sexual reproduction has its “advantages”: the resulting individuals carry the characteristics of both parents and this species of animal will not disappear; they adapt better to their environment.

Also found among animals parthenogenesis is a single form of sexual reproduction, during which the embryo develops from a single germ cell without any fertilization. Such reproduction is usually characteristic of insects, some crustaceans and worms.

Asexual reproduction is a process in which the next generation develops from somatic cells without the participation of reproductive cells - gametes. This type of propagation is usually used in less complex organisms.

For example, an amoeba is divided into two parts. This type of asexual reproduction is called binary fission. This is a very fast and efficient way for bacteria and similar types of cells to create offspring.

Dioecious animals

There are many dioecious animals. But among the lower ones there are many species that have both male and female sex glands. These animals are called hermaphrodites. These include many flatworms: liver flukes, bovine tapeworms, pork tapeworms and others.

After fertilization, a series of developmental stages occur during which the primary germ layers are established and reorganized to form the embryo. During this process, animal tissues begin to specialize and organize into organs and organ systems, determining their future morphology and physiology.

Development- This is the process of formation of the body, closely related to growth. There are two types of animal development: direct and indirect or with reincarnation.

Direct type of development- this is the development of daughter organisms very similar to adults. This includes arachnids, reptiles, birds, mammals, and worms.

Indirect type of development- this is the development in which a larva is created, which differs from the body of an adult individual in both external and internal structure, the nature of movement, and feeding. This includes insects, amphibians, and coelenterates. In the case of indirect development, larvae and adults live in different conditions and therefore do not compete with each other for territory and food. Due to this, a species can have a large number of individuals. For example, in butterflies, larvae eat plant leaves, while adults feed on flower nectar. The toad larva feeds on single-celled algae, while adult toads feed on insects and their larvae. Accordingly, the indirect type of development gives the body significant advantages.

Each animal has its own life cycle with its own developmental phases. Exists simple And complex cycle. The complex life cycle is characterized by alternation of generations (one generation of the liver fluke reproduces sexually, the other asexually) or is associated with the reincarnation of the organism. For example, grasshoppers have a simple cycle: egg - larva - adult insect. But butterflies have a complex life cycle: egg – larva – pupa – adult.

Bark beetle larva

Larvae often constitute a life stage that is used for feeding or dispersal. In many species, the larval stage is the longest, and the adult stage is a short stage solely for reproduction. For example, silkworm moths have adults without mouthparts and cannot feed. And the larvae must eat enough to survive and eventually mate. Indeed, most female moths, once they emerge from their pupa, fly only once to lay their eggs. Then they die.

Many animals have regeneration– restoration of lost body parts. The smallest part of a hydra can give rise to a new organism. Among chordates, regeneration is best developed in amphibians, slightly less so in reptiles (they can renew fallen tails). In other animals, this function remains at the level of wound healing.

Each animal is characterized by its own individual development with such stages:

— embryonic (from fertilization to birth);

- immature;

- sexually mature adult;

- aging and death.

The role of Homeobox (Hox) genes in animal development

Since the early 19th century, scientists have noted that many animals, from simple to complex, have similar embryonic morphology and development. It is surprising that the human embryo and the frog embryo, at a certain stage of embryonic development, appear remarkably similar. For a long time, scientists did not understand why so many animal species looked the same during embryonic development, but became completely different when they matured. At the end of the 20th century, a certain class of genes was discovered that dictate the direction of development. These genes, which determine the structure of animals, are called "homeotic genes." They contain DNA sequences called homeoboxes with specific sequences called Hox genes. This family of genes is responsible for determining the overall body plan: the number

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