Comparative characteristics of monocots and dicots

  Monocots Dicots
Number of cotyledons
Number of petals 3n 4n or 5n
Arrangement of veins Parallel Branched out
Root system Diffuse Tap
Location of bundles Scattered In circle

Summary and test questions

Test questions - 1

1. In what ways are green algae and modern land plants similar?

2. Why is lignin important for the survival of modern land plants?

3. What limitations do bryophytes have due to the fact that the structure of the plant has no vascular tissue?

4. Importance of mosses.

5. What are antheridia and archegonia?

6. Life cycle of mosses.

Test questions - 2

1. What is the main difference between the structures of ferns and mosses?

2. What does the body of ferns consist of?

3. Why ferns can survive outside the water?

4. What is peculiarity of the life cycle of ferns?

5. Structure of spore-bearing organs and peculiarity of gametophyte.

Test questions - 3

1. What are peculiarities of seed plants reproduction?

2. What are main differences between Gymnosperms and Angiospems?

3. What do you know about Conifers?

4. What do you know about Gnetales?

5. What do you know about Ginkgoes?

6. What do you know about Cycads?

Test questions - 4

1. Physical structure.

2. What kinds of plant tissues do you know?

3. Reproductions from Roots, Leaves and Stems.

4. Angiosperm life cycle.

5. Cortex.

6. What are main differences between monocots and dicots?

 


 


ZOOLOGY

Outline: The basis of modern zoology; Philum Protozoa: classification, structure, reproduction; common characteristics of main representatives of phylum Protista; special features of the structure; different ways of reproduction, introducing the Invertebrates, Phylum Sponges, general characteristics of main representatives of Phylum Coelenterata, the specialities of structure and feeding, schemes of development and reproduction, spreading and role in nature, Phylum Plathelminthes: flatworms. Phylum Nemathelminthes: roundworms. Phylum Annelids: segmented worms. General characteristics, specialities of structure, feeding and reproduction. The variety of parasitic worms and fighting against them; the general characteristics and classification of Molluscs. The specialities of structure and living of Molluscs, their role in nature and human life; General characteristics, specialities of morphology and physiology, reproduction and scheme of development; the variety of Phylum Arthropoda and their ecological importance; general characteristics of Chordata and Vertebrata. The systematization of fishes, general characteristics, internal skeleton, circulatory system, nervous system, reproduction, development, physiology and fish behavior, environmental factors; General characteristics and representatives of Amphibians. Outer and inner structure of Anura, Urodela and Apoda. Physiology and behavior of main representatives of Amphibians; General characteristics of reptiles and their representatives. Outer and inner structure. Physiology and behavior; general characteristics of birds class; organs and systems structures; season phenomena in birds’ lives and their adaptation to different conditions of life, migrations; General features and class systematization; characteristics of organs and systems, reproduction and development; mammals’ role in nature and human life; problems of animals’ protection; seasonal phenomena in the mammals’ life, their behavior and taking care of the young.

Zoology is a branch of general biology. Zoology is a science, which studies animals, their structure, functions, levels of organization, peculiarities of their lifestyles. Animals can be found in various habitats: water, land and air. Animals are of great importance. Along with other living organisms they participate in general biosphere processes, which provide biological life cycle of matter. As the greater part of animals are consumers of organic matter, they make the biological processes quicker and contribute to spreading organic matter and energy in biosphere.

Defining zoology as a science we should admit that the purpose of zoology is a wide study of animals – their structure, way of living, growth, practical use. We need to know what animals and with what purpose are held by people, and which of them can do harm to nature and people. If we know zoology well we can use useful animals and fight with harmful ones.

It is very interesting to speak about common features and differences of animals and plants. They have common ancestry, so they have a lot in common in their structure and way of living. Both of them consist of cells and have the same chemical composition. Besides, the substance exchange, heredity, variability, irritation and many other things may be named as the common features of plants and animals.

But they have some differences, too. They are nutrition pattern, stages of growth. Besides, animals don’t have some systems of organs. So, to know this you should study zoology.

Like all other protists, the animal-like protists are made of only one cell and have a nucleus. But they do not have a cell wall, they are not green and they cannot make their own food.

Animals are many-celled heterotrophs.They depend directly or indirectly on their nourishment of land plants or algae. Most digest their food in an internal cavity, and most store their food as glycogen or fat. Their cells do not have walls. Most move by means of contractile cells (muscle cells) containing characteristic proteins. Reproduction is usually sexual. Most are fixed in adult size and shape, in contrast to the plants, in which growth often continues for the lifetime of the organism. The higher animals – the arthropods and the vertebrates – are the most complex of all organisms, with many kinds of specialized tissues, including elaborate sensory and neuromotor mechanisms not found in any of the other kingdoms.

More than 90% of the different species of animals are invertebrates, that is, animals without backbones and most of these are insects.

The invertebrates are also of great ecological importance, particularly the insects.

There are seven classes of vertebrata: the fish (comprising three classes), the amphibians, the reptiles, the birds, and the mammals.

Vertebrates have a closed circulatory system that is quite different from the open circulatory system of insects and other invertebrates. In vertebrates a complex heart pumps blood to all parts of the body through tube blood vessels. Vertebrates’ hearts are not the same. For example, a fish’s heart has two chambers. Amphibians’ heart has three chambers. Birds and mammals have four-chambered hearts.

Vertebrates have well-developed nervous system. The nervous system includes a spinal cord, nerves, and the brain. Vertebrates also have well-developed sense organs, such as eyes and ears. Nerve carries signals from sense organs to the brain. Vertebrates are constantly receiving and reacting to messages about their surroundings. The brain of vertebrates is larger and more developed than the brains of animals without backbone.

The phylum Chordata comprises three subphyla: the Cephalochordata, or lancelets, which includes Amphioxus; the Tunicata, or tunicates, of which the most familiar are the sea squirts; and the Vertebrata, or vertebrates.

Chordates are animals having at some stage a notochord, pharyngeal gill slits, and a hollow nerve cord on the dorsal side.

The second chordate characteristic is the nerve cord, a hollow tube that runs beneath the dorsal surface of the animal above the notochord.

The third chordate characteristic is a pharynx with gill slits. The pharyngeal gill slits become highly developed in fishes, in which they serve a respiratory function, and traces of them remain even in the human embryo.

The fourth characteristic is a tail, block of muscles around an axial skeleton posterior to the anus.

Man is one of a small minority of chordates that do not have a tail.

Phylum Protozoa

The Protozoa – “first animals” – are one-celled heterotrophs possessing typical cellular structures. Classically, the Protozoans have been treated as a single phylum within the Animal Kingdom. But the unicellular level of organization is the only characteristic by which the phylum can be described; in all other respects the phylum displays extreme diversity. Protozoans exhibit all types of symmetry, a great range of structural complexity and adaptations for all types of environmental conditions. As organisms, the protozoans have remained at the unicellular level, but have evolved along numerous lines through the specialization of parts of the protoplasm. That is, specialization has occurred through the evolution of organelles. Protozoan evolution parallels that of multicellular animals in which specialization has occurred through the differentiation of cells within a multicellular body.

Protozoans occur wherever moisture is present—in the sea, in all types of fresh water and in soil. There are commensal, symbiotic and many parasitic species. In fact, the sporozoans are entirely parasitic. Although most protozoans occur as solitary individuals, there are numerous colonial forms. Both solitary and colonial species may be either free-moving or sessile.

The great majority of protozoans are microscopic. Plasmodium, the malarial parasite, is so small that it occupies only 1/4 or 1/5 of a human red-blood cell. At the other extreme, the freshwater ciliate, Spiroslomum, may reach a length of 3 mm. and be seen with the naked eye. The protozoan body is usually bounded only by the cell membrane. The rigidity or flexibility of the protozoan body is largely dependent upon the nature of the underlying cytoplasm. This cortical cytoplasm is usually gelatinous and called ectoplasm, in contrast to the more fluid, internal cytoplasm called endoplasm. Nonliving external coverings or shells occur in many different groups. Such coverings may be simple gelatinous or cellulose envelopes; or they may be distinct shells, composed of various inorganic materials or sometimes foreign particles cemented together.The nucleus is most commonly vesicular containing considerable nucleoplasm and one or more nucleoli.

Characteristic of many protozoans is an organelle called the contractile vacuole. Contractile vacuoles are water-balancing structures acting as pumps to remove excess water from the cytoplasm. These usually spherical vacuoles periodically collapse, releasing their fluid contents to the outside. Contractile vacuoles are most commonly encountered in freshwater protozoans with cytoplasm hypertonic to the aqueous environment. However, contractile vacuoles are also present in some marine groups.

All types of nutrition occur in protozoans. Some are autotrophic, and others are saprozoic; many are holozoic, and digestion occurs intracellularly within food vacuoles. Intracellular digestion has been most studied in amoebas and ciliates.

Gas exchange occurs by the diffusion of oxygen across the cell membrane. Protozoans that live in water where there is active decomposition of organic matter, or live in the digestive tract of other animals, can exist with little or no oxygen present. Some protozoans are facultative anaerobes, utilizing oxygen when present but also capable of anaerobic respiration. Metabolic wastes are diffused to the outside of the organism. Ammonia is the principal nitrogenous waste, and the amount of protein consumed.

The protozoan reproductive processes and life cycles are varied.

Asexual reproduction occurs in all protozoans and is the only known mode of reproduction in some species. Division of the animal into two or more daughter cells is called fission. When this process results in two similar daughter cells, it is termed binary fission; when one daughter cell is much smaller than the other, the process is called budding.

Sexual reproduction may involve fusion (syngamy) of identical gametes (called isogametes), or gametes that differ in size and structure. In ciliate protozoans there is no formation of distinct gametes; instead two animals adhere together in a process called conjugation, and they exchange nuclei.

Encystment is characteristic of many protozoans, including the majority of freshwater species. In forming a cyst, the protozoan secrets a thickened envelope about itself and becomes inactive. Depending on the species, the protective cyst is resistant to desiccation or low temperatures, and encystment enables the animal to pass through unfavorable environmental conditions. The simplest life cycle includes only two phases: an active phase and a protective, encysted phase.

Classification of the Protozoa into three of their major groups is based upon their characteristically different methods of locomotion:

1) by flagellar movement (the zooflagellates — “animal flagellates” — or mastigophores),

2) by pseudopodia (thesarcodines),

3) by ciliary movements (the ciliates).

The fourth major group, the sporozoans, are nonmotile during the major phases of their lives and all are parasites.

5.1.1. Class Mastigophora

The superclass Mastigophora (or Flagellata) includes those protozoans that possess flagella as adult locomotor organelles; it is generally considered to be the most primitive of the major protozoan groups. Since flagellates cannot make their own food, most of them take in tiny pieces of food from the water where they live. But some are parasites. These flagellates live on or inside other living things and feed on them. Many cause disease. Mastigophorans are conveniently divided into the phytoflagellates and the zooflagellates.

The zooflagellates(class Zoomastigophorea) possess one to many flagella, lack chromoplasts and are either holozoic or saprozoic. The zooflagelates are regarded as the most primitive of the Protozoa and also as a link between the algae and the protozoans. They are thought to have been derived from photosynthetic forms. Some are free-living, but the majority of species are commensal, symbiotic, or parasitic in other animals, particularly arthropods and vertebrates. Many groups have become highly specialized. It is generally agreed that this division does not represent a closely related phylogenetic unit. The zooflagellates have probably evolved from a number of different holophytic groups through the loss of pigments. The zooflagelates multiply asexually by mitosis and cell division. The parasitic forms include Trypanosoma gambiense, a flagellate that causes African sleeping sickness, and members of the genus Trichonympha, complex and beautiful flagellates that live as symbionts in the digestive tracts of termites where they digest the wood ingested by the termite.

 

5.1.2. Class Sarcodina

 

 

The sarcodines are amoeba-like organisms which have no coat or wall outside their cell membranes and which generally move and feed by the formation of pseudopodia. They move by changing shape. The shape changes to form fingerlike parts known as pseudopodia, or “false feet”. For the amoeba to move in another direction, it must form new pseudopodia on that side of the body. Despite their uncomplicated appearance, they are complex cells and are even capable of some complex behavior patterns, as when sensing and pursuing prey organisms. Amoebas take in food by forming pseudopodia around each peace of food. When the food is surrounded, a food vacuole is formed around it and it is moved inside the cell. Reproduction may be sexual or asexual. Many of the sarcodines cover their amoeba-like characteristics with firm bright shells. Their shells are made of calcium carbonate, extracted from water. It is possible to date a particular stratum by the type of Foraminifera that it contains, a fact that has proved of immense practical value in locating oil-bearing strata in Texas, Oklahoma and many other oil-rich areas.

Some cause amoebic dysentery.

 

5.1.3. Class Ciliatea

 

The subphylum Ciliophora has only one class, the Ciliatea. This is the largest and the most homogeneous of the protozoan classes.

The ciliophores, or ciliates, are the most highly specialized and complicated of the Protozoa, and indeed probably represent the most complex of all living cells. They are characterized by cilia. The rows of cilia are called cirri, which can be used for walking or jumping. Cilia, membranelles, and cirri move in a coordinated fashion. Most ciliates possess a cell mouth or cystosome.

Most ciliates live in freshwater or seawater. They do not have any parts to help them move. Instead, they move by changing shape. They move by means of many short hair-like parts called cilia.

Perhaps the best known ciliate is the Paramecium. It is shaped like the sole of a slipper. It has a long groove on one side. The groove is lined with cilia that help pull food along the groove and into the mouth-like gullet. At the end of the gullet, a bubble-like food vacuole forms around the food. When the vacuole is full, it carries the food into the cell where the food is broken down

Cilia have the same structure as do flagella; they differ from flagella chiefly in that they are generally more numerous and are considerably shorter. Compound ciliary organelles, evolved from the adhesion of varying numbers of individual cilia, are of common occurrence.

Some ciliates also have myonems, contractile threads. All have a complex skin, the cortex, which includes the cell membrane. In some groups, the cortex contains small barbs known as trichocysts, which are discharged when the cell is stimulated in certain ways. The ciliates have another unusual feature: they have two kinds of nuclei, macronuclei and micronuclei. One or more of each kind is present in all cells. They also have a complex system for exchange of genetic information, in which cells conjugate and the macronuclei undergo meiosis. The macronucleus in certain ciliates contains 50 to 100 times as much DNA as the micronucleus and so is believed to represent multiple copies of it.

The body shape is usually constant and in general is asymmetrical. The ciliate body is typically covered by a complex, living pellicle, usually containing a number of different organelles.

Mucigenic bodies are the group of pellicular organelles found in many ciliates. They are arranged in rows like trichocysts and discharge a mucoid material that may function in the formation of cysts or protective coverings.

About 6,000 species of ciliates are known, both freshwater and saltwater forms. Almost all are free-living (non-parasitic).

 

Class Sporozoa

 

The fourth class of Protozoa is the Sporozoa, all of which are parasitic. They are characterized by the lack of cilia of flagella in adult forms and by their complex life cycle. A single sporozoan undergoes multiple fission, dividing into numerous smaller cells (the spores) simultaneously.

The sporozoans are parasitic protozoans which were formerly united within one class, the Sporozoa, because of the presence of sporelike infective stages in some members of both groups. The presence of flagellated gametes, the ability to move by gliding or body flexions, and the possession of pseudopodia as feeding organelles in different groups suggest a relationship to the flagellates and to the sarcodines.

The subphylum Sporozoa contains the most familiar of the sporozoan parasites—the gregarinesand the coccidians. The coccidians infect the intestinal or blood cells, and include the parasites causing human malaria and the coccidioses of domestic animals. Species of Sporozoa are widespread and parasitize vertebrates and most invertebrate phyla.

The life cycle is complex. It can be divided into three phases: schizogony, an asexual multiplication of the parasite following infection of the host; gamogony, the development of gametes; and sporogony, also a multiplication and an infective stage, typically a spore.

The best known sporozoans are members of the genus Plasmodium, which cause malaria. Plasmodium is passed back and forth between man and the Anopheles mosquito. The female mosquito requires blood for the development of her eggs. If the female draws her blood from a person with malaria, she will pick up Plasmodium cells which multiply within her body, although they do not harm her, and travel in her salivary glands. When she bites her next victim, she injects a droplet of salivary fluid under his skin. This fluid seems to anesthetize the victim against the bite; it also keeps the blood from clotting so that it will flow freely through her fine proboscis. Ultimately, through an inflammatory reaction, it raises the familiar welt. This drop of salivary fluid also carries Plasmodium, which eventually enter the blood cells and begin to multiply. The Plasmodium break out of the blood cells at regular intervals – usually every 48 or 72 hours, depending on the species – that is why malaria is characterized by recurrent bouts of chills and fever.






Дата добавления: 2016-07-18; просмотров: 1371; ЗАКАЗАТЬ НАПИСАНИЕ РАБОТЫ


Поиск по сайту:

Воспользовавшись поиском можно найти нужную информацию на сайте.

Поделитесь с друзьями:

Считаете данную информацию полезной, тогда расскажите друзьям в соц. сетях.
Poznayka.org - Познайка.Орг - 2016-2022 год. Материал предоставляется для ознакомительных и учебных целей.
Генерация страницы за: 0.061 сек.