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Animals are a large group of multicellular eukaryotes, but they are different from microorganisms.

Animals can't synthesize organic matter from inorganic matter, but can only treat organic matter as food, which can be eaten and relied on. They are composed of cells with nucleus, no cell wall, movement and substrate.

Therefore, animals have different morphological structures and physiological functions from plants from feeding, digestion, absorption, breathing, circulation, excretion, feeling, exercise to reproductive life activities.

Zoology classifies animals with the same or similar characteristics into the same category according to their morphology, internal structure, embryonic development characteristics, physiological habits and geographical environment.

Mainly divided into two categories: chordates and invertebrates; According to aquatic or terrestrial animals, it can be divided into aquatic animals and terrestrial animals; According to whether there are feathers, it can be divided into feathered animals and featherless animals; According to whether there is a spine in the body, we can divide all animals into vertebrates and invertebrates.

After the appearance of primitive life, with the change of living environment, millions of species have appeared and died out one after another, and only those species that can adapt to environmental changes have survived and multiplied to this day. The process of continuous evolution of this species is biologically called evolution.

Animals are a major group of living things, called animals.

Animal perspective

They can respond to the environment and move, preying on other creatures. According to the current genetic research results, the ancestors of animals should come from a collection of various protozoa and then undergo cell differentiation, rather than from a polynuclear protozoa.

The life of metazoa that reproduce through sexual reproduction can be artificially divided into three stages: pre-embryonic development, embryonic development and post-embryonic development. The basic structure of animal body is fixed in the development process, especially in the early embryo, and some of them will undergo metamorphosis later.

If two animals of different species have the same ancestor, they will show some similarities in the embryonic development stage. However, after entering the post-embryonic development stage, in order to adapt to the environment, they will develop some special organs or functions.

Most animals are active. They can move spontaneously and independently. Most animals are consumers, and they depend on other organisms (such as plants) for food. However, a few animals belong to decomposers-they feed on dead organisms (organic matter) (such as earthworms).

Animals have all kinds of behaviors, which can be regarded as animals' responses to stimuli. Behaviorism is the science of studying animal behavior. The famous behavior theory is the instinctive theory put forward by Connard Lorenz.

Development history

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Animal species

The earliest animals and marine animals

Most animals known to appear in fossils are marine species during the CAMBRIAN explosion 540 million years ago. The CAMBRIAN explosion is a great challenge to evolution.

The ocean is the largest ecological group on the earth, and it is the first place where life breeds on the earth. Early life on earth only existed in an environment with water.

The earliest animals and marine animals were invertebrates. It was not until 500 million years ago that one of the earliest vertebrates, the head turtle, appeared in the ocean.

The earliest amphibians

The earliest amphibians are vertebrates that evolved from fish, and their tails and scales are similar to fish scales. They mainly live in the ocean and sometimes walk on land.

Early reptile

The earliest reptiles appeared in the Carboniferous and evolved from amphibians. They like to live in dry places and expand their activities rapidly. They can be seen everywhere on the earth, such as dinosaurs.

The appearance of mammals

Compared with reptiles, early mammals were small and not strong. However, when dinosaurs and other reptiles became extinct, mammals expanded their habitats and gradually dominated the land, and their postures began to develop in a diversified direction. ? [ 1]?

Classification and characteristics

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Animals (2 pieces)

Due to the variety of animals, human beings still lack in-depth research and understanding of some groups, so until now there is no perfect animal classification system in the world. The difference is because some scholars upgraded some different classes to phylum, such as rotifer, abdominal hair, moving kiss, linear, nematode and other animals in the original prosthesis cavity, and some scholars upgraded them to phylum.

In addition, some new taxa have been found, which are not suitable for the original door, so they are simply newly established as a separate door, such as Ctenomedusae, that is, because Ctenomedusae was found. For the study of medicinal animals, pharmacology 1960 was divided into 10 in the early stage, and later Chinese medicine identification was adopted 1977. The animal kingdom is still divided into 10.

According to the characteristics, it is still: cell differentiation, germ layer formation, the presence or absence of body cavity, morphological symmetry, body segment division, bone properties, appendage characteristics, the occurrence and development of other organ systems, and the strata are divided with reference to geological data.

invertebrate

Although invertebrates are a lower group in the animal kingdom, they are an incredibly diverse animal species. Invertebrates far exceed vertebrates in both species and quantity. In a wide variety of animal kingdom, invertebrates account for more than 90%, including not only jellyfish, octopus and other animals in the ocean, but also various insects and parasites.

Features:

1. Species system: Invertebrates are a diverse species system. Apart from their spines, they have almost no other common features, only a little different kinship. All kinds of invertebrates have different forms and lifestyles.

2. Life cycle: Different kinds of invertebrates have different life cycles. Most invertebrates are egg-laying animals, and some need to go through various larval forms, such as butterflies, moths and other insects; Others become adults as soon as they hatch.

3. Exercise habits: Most invertebrates have obvious front and back ends, and the sensory organs are gathered near the mouth. This structure can help them find new situations in time when they move forward, and take countermeasures quickly to make their actions faster and more agile.

4. Linked body: Many invertebrates have a body that can be divided into several separate links, which is beneficial for them to change their shapes at will and move in complex ways. Scolopendra, for example, has a pair of legs in most links and is extremely flexible when exercising.

Including:

I. Native types

Single-celled animals, with very simple body structure, can eat, move, reproduce and die. An animal whose body is so small that it can only be observed with a microscope. Habitat in fresh water, sea water or other animal body fluids. Such as amoeba.

Including:

1. Protozoa: All single-celled animals are the most primitive animals. A few gather in groups, live in water or wet soil, and some are parasitic, asexual or sexually propagated. There are no species of medicinal animals in this phylum, but it is a primitive group in evolution and is closely related to human life. Some parasitic species will do great harm to human health and the reproduction of economic animals. Such as euglena, paramecium, etc. ;

2. Nematode: a simple internal parasite with few recorded species;

3. Orthoptera: rhomboid-like animals;

4. Polypodiaceae: also known as Polypodiaceae, sponges are primitive multicellular animals;

5. Platycladus: Up to now, this phylum is monopolized by an animal, filariasis;

6. Archaea: As the name suggests, "Archaea" means that such animals are extinct, and "cups" mean that they look like cups;

7. Acanthoptera: including hydra, jellyfish, anemones and corals;

8. Ctenomedusae: Some people also classify this phylum as Ctenomedusae.

Second, worms.

Any of various invertebrates having a slender and flexible body and usually no appendages. Worms belong to several invertebrates, including Platycladus orientalis, Annexus, Neoptera, Marsupials, Starfish, Ladybugs, Echinocephala, Brachiopoda and Chaetognathus.

Features:

1. The body is soft and divided into links, and each link has a pair of excretors. Such as earthworms and nereis.

2. Soft and round body, parasitic in animals or plants. Such as roundworms and pinworms.

Including:

1. Platycladus orientalis: there are worms, trematodes, tapeworms and other parasites;

2. annelids: including earthworms, leeches, nereis, etc.

3. Insecta: marine benthos with cylindrical or long sacs;

4. Newtonian fauna: similar animals are slightly higher than flat animals;

5. Nematoda: A huge family, including Ascaris, etc.

6. Linear phylum (marsupial phylum): a class of animals similar to nematodes;

7. Stellaria: similar to tabanidae;

8. Echinocephala: an animal with a kiss in the front of its body;

9. Polypodiaceae: it mostly lives on the seabed below 200 meters, looks like a worm and has a slender body;

10. Chaetognathus: There are only about 50 species, and they are also marine animals.

Third, the software category.

Mollusks are a very successful biological category with various shapes, including all "shellfish", octopus and squid. Most mollusks live in the sea, some live at the junction of salty fresh water or fresh water, and some live on land.

Including:

1. Mollusca: It includes a large number of common animals, such as snails, snails, oysters and octopus.

2. Mollusca; Has become extinct.

Four, arthropods

Arthropoda: animals that account for more than two-thirds of the animal kingdom, as well as insects, spiders, crabs and so on. All belong to this door.

Main features:

1. The two sides of the body are symmetrical, and the body is segmented, but some body segments merge into special parts, such as the head and chest. Some arthropods, such as spiders, further fuse their heads and chests into one head and chest. The appendages of the body, such as feet, tentacles and mouthparts, are segmented.

2. The body wall is hard, mainly composed of chitin, which can provide protection and can also be used as an exoskeleton. Arthropods need to molt many times during the growing period, because the body wall is hard and hinders growth.

3. The sensory system is very developed, and there are two kinds of eyes: monocular and compound. Compound eyes are used for seeing, while monocular eyes are used for perception. In addition, there are organs of touch, taste, smell, hearing and balance, and many insects also have special vocal organs.

4. The respiratory system is quite diverse. You can use the body surface, gills (aquatic) and trachea (terrestrial) to breathe. Spiders and other animals breathe with their lungs.

Verb (short for verb) others

Including:

1. Podopoda: including CAMBRIAN shrimp, etc.

2. Tardigrada: a strong animal that can tolerate high temperature, absolute zero, high radiation vacuum and high pressure;

3. Clawed animals: the body is worm-shaped, the foot is cylindrical, and there are claws at the end, which is almost extinct;

4. Gastropoda: animals with cilia on the ventral surface;

5. rotifer: very small, similar to protozoa;

6. Branchlets: marine benthos living in cold water near the poles, with few recorded species;

7. Kissing animals: similar to gill dragging animals;

8. Armored fauna: a new phylum discovered only in 1983, without accurate classification;

9. Internal anus: small moss animals;

10. Circadian rhythm: a newly discovered animal;

1 1.Linguata: they are all bloodsucking parasites, and their taxonomic status is still difficult to determine;

12. Micrognathus: 1994 A newly discovered animal, about which human beings know little;

13. Gastrognathus: very small, living in fine sand in shallow water, people don't know much about it;

14. brachiopods: Sometimes you will see some shell-like fossils left by this kind of animals in street stalls;

15. Extraanal fauna: It used to be the same phylum as the intra-anal fauna, called bryophytes, but now it is separated;

16. Lepidoptera: a very small phylum with only 10 species of animals, all of which are marine benthos;

17. archaea: extinct in the big bang 530 million years ago, only discovered in recent years;

18. Echinoderms: including starfish, sea urchins, sea cucumbers and sea lilies;

19. Polypodiaceae: a non-parasitic animal with no mouth and digestive tube, living in the deep sea, and its taxonomic status is controversial;

20. Omnivorous: only two species, distributed near the Baltic Sea, were once considered platypus and mollusk;

2 1. Hemichordates: The body is worm-like, and some people classify it as chordates.

Tailrope animals and cephalochordates

All living things belonging to the suborder Chordata; Chordata and Cephalotaxus. Between invertebrates and vertebrates.

vertebrate

That is, all living things in the vertebrate subfamily of Chordata.

The most striking feature of vertebrates is that the spine or spine supports the body. Typical vertebrates have complex sensory organs and a brain that connects muscles and limbs. The complex bones inside enable vertebrates to grow quite large and have strong adaptability.

Vertebrates account for only a small proportion in the animal kingdom. There are about 40,000 known vertebrates, which are divided into fish, amphibians, reptiles, birds and mammals. They can be found in almost every corner of the earth.

Main features:

1. Skeleton: The skeleton of vertebrates is mainly composed of spine, limbs and skull. The spine is the main supporting part of vertebrate bones. The skull can protect the brain, and the heart, lungs and other internal organs are wrapped between the spine and ribs.

2. Limbs: Many vertebrates have limbs. Fish paddle by fins, and the limbs of terrestrial animals evolved from fins. The limbs help vertebrates swim, walk or fly around.

3. Skin: The skin of vertebrates is scaly, sticky, hairy or feathery, and different types of skin have different functions. Squamous skin can help fish protect their bodies; Sticky skin can help amphibians breathe on land; Hairy skin can help birds and mammals keep out the cold.

4. Feeling: Different kinds of vertebrates have their own unique sensitive senses to help them detect danger, foraging or courtship, such as sight, hearing, touch, taste, smell, echolocation and sensitivity to electricity, magnetism and gravity.

5. Reproduction: There are two reproductive modes in vertebrates: one is sexual reproduction, that is, male and female animals mate, and female eggs can only reproduce after male fertilization; The other is asexual reproduction, because a few vertebrates have no gender distinction. ? [2]?

Including:

I. Fish (5 types)

1. Blind Eel: Blind eels live in the deep sea, almost completely blind, with a slender body and hermaphroditism.

2. lamprey: As the name suggests, lamprey has seven pairs of gills. They belong to the same class as blind eels. The body is slender, the sucker is big, and the shape is very similar to that of ordinary eels.

3. Cartilaginous fish: Similar to bony fish, but without swim bladder and scales, they are usually large, only live in the ocean and have developed teeth. Endoskeleton is completely composed of cartilage, usually calcified, but there is no real bone tissue.

4. Leptospira: It belongs to teleost superfamily with Actinidia. It has a history of more than 400 million years, and now most species have become extinct. It is characterized by the axial bone on the fin, so some fleshy fish can live out of water for a long time.

5. Kiwifruit: There are more than 30,000 kinds of Kiwifruit. There are both fresh and salt water. There are swim bladders and scales, and the fins are radial. Most people can't live without water.

Although the above five categories are all called "fish", they are actually very different.

Second, amphibians

frog

That is, there are more than 4000 species of amphibians, including Anpoda, Anura and Anura.

Features:

1. You need to spend your childhood in the water.

2. It has a skeleton structure adapted to land, with limbs, moist skin and many glands.

3. The body has no scales and body hair.

4. The tongue is forked, inverted and can extend outward.

5. Both mating and fertilization are carried out in water.

6. Larvae breathe through gills, while adults breathe through skin, inner wall of mouth and lungs. ? [3]?

Third, reptiles

Reptiles are vertebrates that are completely adapted to land life. Compared with amphibians, they have dry scaly skin that reduces water loss, including scales, turtles, crocodiles and so on.

Features:

1. The body surface is covered with scales or horny plates;

2. Exercise adopts a typical crawling mode, that is, the limbs extend outward, the abdomen touches the ground and crawls forward.

Everyone breathes with his lungs, and his body temperature is not constant, but will change with the change of outside temperature, so he should hibernate in cold winter and sleep in hot summer.

Reptiles are cold-blooded animals with thorns, and their bodies are covered with scales.

Reptiles have only three ventricles in their hearts, unlike other animals, which have four.

6. Most reptiles are oviparous, but some kinds of eggs hatch in the mother before birth. ? [3]?

Including:

Fourth, birds

That is, birds are generally thought to have evolved from reptiles. Birds can live anywhere in the world because they can fly. There are more than 9000 species of birds in existence.

Main features:

1. The body is covered with feathers, has wings and can fly. The skin is thin and soft, which is beneficial to the strenuous exercise of muscles.

hawk

2. The metabolism is vigorous and the body temperature is constant. Persistent high body temperature promotes the speed of metabolism in the body. Constant temperature reduces the dependence of animals on external temperature conditions and gains the ability to move and survive at night in the polar continent.

3. Have developed nervous system and senses. Birds have developed brains, cerebellums and midbrains. The cerebral hemisphere is larger, which is mainly due to the increase of striatum at the bottom of the brain. In birds, the striatum is an advanced part of sports management, and it is also related to some complicated living habits. Experiments show that after a part of striatum is removed, its normal excitement and inhibition are destroyed, vision is affected, and courtship and nesting habits are lost. Birds have underdeveloped cerebral cortex and developed cerebellum, which is related to the coordination and balance of bird flight movements.

4. It has perfect breeding methods and behaviors (nesting, hatching and brooding).

Including:

1. Flat-chested suborder: strong hind legs, flat chest, no keel process, no flight ability; Feathers are distributed all over the body, and there are no feather areas and bare areas. Feather branches have no hooks, so they don't form feathers. The common species is ostrich.

2. Penguinoidea: medium and large birds living in diving, with a series of characteristics adapted to diving life. The forelimbs are fin-shaped and suitable for paddling. Scaly feathers (depending on short feather axis and narrow feather) are evenly distributed on the body surface. The tail is short, the legs are short and move to the back of the body, and there is a bun between the toes to adapt to swimming life. When walking on land, the body is almost upright and swings from side to side. The subcutaneous fat is developed, which is conducive to maintaining body temperature in cold areas and water. The bone is heavy and has not expanded. The sternum has a well-developed keel-like process, which is related to the forward stroke. Swim fast. The distribution of this use is limited to the equator and the southern hemisphere. On behalf of emperor penguins.

3. breastplate: usually with developed wings and good at flying, the keel suddenly reaches, and the last 4 ~ 6 coccyx vertebrae heal into one coccyx. Generally, it has an inflatable skeleton, and normal feathers develop well to form feather pieces. The body surface is divided into feather area and bare area. Most males have no mating organs. There are many kinds of birds in this category. In order to facilitate research, we can discuss their groups from two aspects:

One aspect is divided into:

Birds: Beaks are flat, wide or pointed, legs are short and webbed, and wings are strong or degenerate.

Wading birds: long and thin beaks, long feet and toes, undeveloped fins and strong wings.

Quail chicken: the peck is short and powerful, the claws are strong, and the wings are short and round.

Pigeons and pigeons: short beak, wax film at the base, short and healthy feet and developed wings.

Crawler: The beak is hard, the feet are short and healthy, the toes are right and the wings are developed.

Raptor: beak is strong and hooked, foot is strong, claws are pointed and hooked, wings are strong and good at flying.

Songbirds: Beaks are different, feet are short and thin, and wings are developed.

On the other hand, it is divided into:

Pelodiformes: move forward everywhere, with a complete poof in the middle; The beak is hooked and has a well-developed laryngeal sac. Young birds belong to late birds and swimming birds, such as cormorants.

Hemiptera: the neck is long, the beak is long, the legs are long, the first three toes are followed by one toe, and the four toes are in the same plane. Young birds are late-maturing birds, involving birds, and common species are egrets.

Zoology: the mouth is flat, the carapace is thickened, and there are comb-like protrusions on the edge; Legs are short and backward, toes are three in front and one in back, webbed between toes, and wing mirrors are often found on male wings; Male birds have mating devices; Young birds are early birds and swimming birds. Common species are swans and wild ducks.

Hawkiformes: the mouth has a pointed hook, developed claws and strong flying ability; Sharp vision, raptors and chicks are all late birds. Common species are kites, kestrels and golden eagles.

Chicken shape order: strong; The beak is short and conical; Short and round wings, good at walking; The male bird has a crown of meat on his head and bright feathers; The behavior during the breeding period is complex, and quail chickens and young birds belong to early adult birds. Such as brown eared pheasant, golden pheasant with red belly, etc.

Crane order: beak is long, neck is long, legs are long, toes are three in front and one in the back, webbed between toes is underdeveloped, and the position of hind toes is high, which is not on the same plane as other three toes. Young birds are early birds, involving birds. Common species are red-crowned crane and gray crane.

Pigeon: short beak with wax film; Four toes in the same plane, short feet, healthy, good at walking; The crops are developed, and the chicks are late-maturing birds or early-maturing birds, which are pigeons. Common species are pigeon, grouse and so on.

Owl: commonly known as owl. The jaw is strong and hooked; The head is big, the eyes are big and forward, and the feathers around the eyes form a face plate; Ear holes are large, with ear feathers and keen hearing; The fourth place can be reversed; Young birds are late-maturing birds, raptors. The main species are long-eared owls and short-eared owls.

? Shape: the mouth is conical, suitable for pecking wood; The tongue has a long horny hook; Toes are two front and two back; Young birds are late-maturing birds, and they are climbing birds. Common species such as spotted woodpecker.

……

Verb (abbreviation for verb) mammal

In other words, all mammals are warm-blooded, and their offspring are one of their most remarkable characteristics.

Including:

1. Protozoa: under the jurisdiction of Monoptera.

2.Euthera: governs Carnivora, Primates, Chiroptera, Artiodactyla, etc.

3. After the subclass Mammalia: there are marsupials.

behaviour

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protect

The defensive behavior of animals is the behavior of animals to respond to foreign aggression, defend their own survival, or warn other individuals in their own group.

Store food

Fundamentally speaking, animals ingest food in order to ingest nutrients that constitute the body-all kinds of organic and inorganic substances, as well as energy necessary for various physiological activities. This is the feeding behavior of animals. Therefore, when there is enough food, some animals will store some food and eat it when they are hungry. This behavior is called food storage behavior.

attack

The aggressive behavior of animals refers to the attack or struggle between individuals of the same species. In the animal kingdom, individuals of the same species often attack or fight with each other for food, spouses, nests and fields.

Reproduction and development

Almost all animals have some kind of sexual reproduction. Mature individuals are diploid or polyploid. They have some special germ cells, which produce smaller swimming sperm or larger resting eggs after meiosis. Sperm and eggs will combine to become fertilized eggs and develop into new individuals.

Many animals can also reproduce asexually. This may occur in parthenogenesis (mature eggs are produced without mating) or in some cases through cleavage.

The fertilized egg will develop into a small ball at first, called an embryo, where it will recombine and differentiate. In the sponge, the embryo will swim to a new position and develop into a new sponge. In most other groups, embryos undergo more complex recombination. Embryos are initially nested to form gastrula with digestive cavity and two independent germ layers-ectoderm and endoderm. In most cases, there is a mesoderm in the middle. These germ layers then differentiate into various tissues and organs.