UNIT 1. BIOLOGY

  1. Text 1. Biological Sciences
  2. Text 2. What is life?

Text 1. Biological Sciences

(from https://en.wikipedia.org)

The life sciences, as the name implies, study living organisms. They also are known as the biological sciences or biology. Alongside physics and chemistry, biology is one of the largest and most important branches of science. At the highest level, biology is broken down based on the type of organism being studied: zoology, the study of animals; botany, of plants; and microbiology, of microorganisms. Each field of biology has contributed to mankind or the Earth’s well-being in numerous ways. Most prominently: botany, to agriculture; zoology, to livestock and protection of ecologies; and microbiology, to the study of disease and ecosystems in general.

Besides classifications based on the category of organism being studied, biology contains many other specialized sub-disciplines, which may focus on just one category of organism or address organisms from different categories. This includes biochemistry, the interface between biology and chemistry; molecular biology, which looks at life on the molecular level; cellular biology, which studies different types of cells and how they work; anatomy, which examines the structure of living things; physiology, which looks at organisms at the level of tissue and organs; ecology, which studies the interactions between organisms themselves; ethology, which studies the behavior of animals, especially complex animals; and genetics, overlapping with molecular biology, which studies the code of life, DNA.

The foundations of modern biology include four components: cell theory, that life is made of fundamental units called cells; evolution, that life is not deliberately designed but rather evolves incrementally through random mutations and natural selection; gene theory, that tiny molecular sequences of DNA dictate the entire structure of an organism and are passed from parents to offspring; and homeostasis, that each organism’s body includes a complex suite of processes designed to preserve its biochemistry from the entropic effects of the external environment.

The basic picture in biology has stayed roughly the same since DNA was first imaged using x-ray crystallography in the 1950s, although there are constant refinements to the details, and life is so complex that it could be centuries or even millennia before we begin to understand it in its entirety. But it should be made clear that we are moving towards complete understanding: life, while complex, consists of a finite amount of complexity that only appreciably increases on relatively long timescales of hundreds of thousands or millions of years. Evolution, while creative, operates slowly.

Text 2. What is life?

(from www.faculty.washington.edu)

The question seems simple enough. But biologists, although they have a vast knowledge of living things, find that the definition of life isn’t always so obvious – sometimes the dividing line between living and nonliving things is quite obscure. For example, a virus is lifeless by itself, because it does not grow, metabolize, or respond to its environment, but it can reproduce once it enters a living cell.

Instead of trying to reach a precise definition of life, scientists focus on the characteristics that seem to distinguish living things. No single characteristic tells us what life is, but together they form a composite that generally sets living things apart from nonliving things. Nearly all living things share the following characteristics:

  • Growth. Growth in living things is more than simply an increase in size. Living things are able to produce organic molecules that become part of their structure.
  • Metabolism. Living things undergo chemical processes to produce the materials and energy necessary for life.
  • Reproduction. Living things are able to produce more of their kind sexually or asexually.
  • Movement. Almost every living thing moves, either by moving from place to place or undergoing internal movements such as circulation or the movement of organs.
  • Responsiveness. Living things react to their changing environments.
  • Adaptation. Most living things are able to adjust to changes in their living conditions. Adaptation helps an organism survive and reproduce in its particular environment.

The two most widely accepted theories of the origin of life are the theory of panspermia and the theory of chemical evolution. The theory of panspermia claims that spores – specialized reproductive cells – from some other part of the universe landed on the Earth and began to develop.

The theory of chemical evolution proposes that life developed through a series of chemical reactions in the atmosphere and oceans early in the Earth’s history. This theory is more widely accepted today than the theory of panspermia.

In order to understand the theory of chemical evolution, we need some knowledge of the elements of life. The most common elements in living things are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. Other elements are present in smaller amounts.

Water, the simplest chemical compound of importance to living things, makes up 50 to 95 percent of most organisms and is an essential part of many life processes. Most chemical reactions within organisms can occur only in a water solution, and water is also a part of many such chemical reactions. In addition, water moves nutrients within organisms.

Most of the principal compounds in living things – except water – contain carbon. Almost all living material consists of about 50 kinds of carbon molecules, plus the macromolecules – large, complex molecules – formed from them. The four main types of macromolecules are carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates consist of carbon, hydrogen, and oxygen and serve as the principal energy source for most living things. Carbohydrates also provide the basic material from which many other kinds of molecules are made.

Lipids consist primarily of carbon and hydrogen. The best-known lipids are animal fats and vegetable oils, both rich sources of energy. Many kinds of organisms store food in the form of lipids. Other lipids form the basic structure of cell membranes.

Proteins are the most common – and most complex – macromolecules in living things. They are important structural parts of the tissues of cells and of the substances between cells. They are also the most varied – human beings have thousands of different proteins. Proteins in the form of enzymes also play an essential role in the control of chemical reactions in the body. Proteins are made up of one or more long chains called polypeptides, which consist of many small molecules called amino acids. All amino acids contain carbon, hydrogen, nitrogen, and oxygen.

Nucleic acids store and transmit the information necessary for producing proteins. They consist of long chains of smaller molecules called nucleotides, which consist of a nucleic base (adenine, guanine, cytosine, or thymine), a sugar, and a phosphate group. There are two types of nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). DNA carries the hereditary information that an organism passes on to its offspring – it determines that a cat will produce a cat, not a dog. DNA has a nucleotide consisting of one of the four bases plus deoxyribose, a form of sugar. RNA, serving as a pattern for building proteins, transmits DNA’s instructions. RNA consists of a nucleotide that has adenine, guanine, cytosine, or uracyl plus ribose, a more complex form of the sugar contained in DNA.

Vocabulary

adenine (A) – аденин
autotroph – автотроф, автотрофный организм (организм, рост и размножение которого не зависят от внешних источников органических соединений)
bladder (urinary bladder) – мочевой пузырь
carbohydrates – углеводы
carbon dioxide – углекислота, углекислый газ
cartilage – хрящ
cavity – полость
cell – клетка
cephalic – головной, расположенный около головы, верхний
cervix – шея; шейка (какого-н. органа)
cytosine (C) – цитозин
deoxyribonucleic acid (DNA) – дезоксирибонуклеиновая кислота (ДНК)
ecosystem – экосистема
enzyme – фермент, энзим
fertilization – оплодотворение, опыление, удобрение
gall bladder – желчный пузырь
guanine (G) – гуанин
heterotroph – гетеротроф, гетеротрофный организм (организм, для роста и размножения которого необходимы экзогенные органические вещества)
homeostasis – гомеостаз(ис) (постоянство внутренней среды организма, ее устойчивого равновесия с внешним миром)
lipid(e) – липид
livestock – домашний скот
lymph node – лимфатический узел, лимфоузел
metabolism – метаболизм, обмен веществ
nucleic acid – нуклеиновая кислота
nucleotide – нуклеотид
nutrient – питательное вещество, нутриент
organogenesis – органогенез (формирование органов во время роста)
ovary – анат. яичник, бот. завязь
pancreas – поджелудочная железа
polypeptide – полипептид
predator – хищник, пожиратель
protein – белок, протеин
puberty – половая зрелость, период полового созревания
reproduction – репродукция, воспроизведение, размножение, воспроизводство, возобновление (растений)
ribonucleic acid (RNA) – рибонуклеиновая кислота (РНК)
spleen – селезенка
thoracic – торакальный, грудной
thymine (T) – тимин
thymus – тимус, вилочковая железа, зобная железа
uterus – (pl. -ri) матка
vertebrate body – позвоночное животное
zygote – зигота, оплодотворенная яйцеклетка


Exercise 1. Give Russian equivalents for the following terms.

1) metabolism
2) nutrient
3) cell
4) fertilization
5) zygote
6) autotroph
7) heterotroph
8) organogenesis
9) puberty
10) reproduction
11) homeostasis
12) predator
13) enzyme
14) protein
15) carbohydrate


Exercise 2. Give English equivalents for the following terms.

1) гетеротрофный организм
2) питательное вещество
3) клетка
4) оплодотворение
5) оплодотворенная яйцеклетка
6) автотроф
7) обмен веществ
8) органогенез
9) половая зрелость
10) размножение
11) гомеостаз(ис)
12) хищник


Exercise 3. Substitute the corresponding terms for the following definitions.

1) deals with plants
2) deals with animals
3) examines the structure of living things
4) deals with the normal functions of living things and their parts
5) studies bacteria
6) investigates how organisms pass on characteristics to their offspring
7) focuses on the structure and function of molecules essential to life
8) studies the origin and development of human cultures and physical characteristics
9) an organism that is able to form nutritional organic substances from simple inorganic substances such as carbon dioxide
10) an organism deriving its nutritional requirements from complex organic substances
11) production and development of the organs of an animal or plant
12) the period during which adolescents reach sexual maturity and become capable of reproduction
13) the tendency towards a relatively stable equilibrium between interdependent elements; esp. as maintained by physiological processes
14) an animal that naturally preys on others

Exercise 4. Translate the terms into Russian/ Belarusian and say which of the sciences (biology, physiology, bacteriology, genetics, anatomy, zoology, botany, molecular biology) they belong to.

Thyroid, cartilage, thymus, adrenal, pituitary, pancreas, pineal gland, ovary, vertebra, thorax, bladder, gall bladder, uterus, allostery, cephalic region, vertebrate body, cavity, thoracic, thymus, lymph nodes, spleen, cervix, small intestine, large intestine, amino acid, enzyme, adrenal, homeostasis, integument, excretory, heterotroph, livestock, DNA, mutation, rodent, anaerobic, genus, meiosis.


Exercise 5. Match the organ system with the function it performs. Translate the terms into Russian.
  • excretory
  • digestive
  • cardiovascular
  • skeletal
  • muscular
  • endocrine
  • respiratory
  • integumentary
  • nervous
  • reproductive (male)
  • reproductive (female)
  • lymphatic
  • ingests and breaks down food so that it can be absorbed by the body;
  • elimination of liquid wastes; regulation of water balance;
  • enables gas exchange, supplying blood with oxygen and removing carbon dioxide;
  • provides mechanical support for the body; mineral storage; red blood cell production;
  • contraction and extension of muscles enables movements, posture, and balance;
  • protects body from environment, injury, and infection; fat storage;
  • transport of nutrients, gases, hormones, and wastes to and from all the cells of the body;
  • secretes hormones into bloodstream for regulation of body activities;
  • senses environment, communicates with and activates other parts of the body;
  • protects against infection;
  • produces eggs, receives sperm from males, and supports the development of offspring;
  • produces and delivers sperm;

Exercise 6. Translate the terms into English and say to what organ systems they belong.

1) mouth, esophagus, stomach, liver, pancreas, gall bladder, small and large intestine
2) kidney, ureter, bladder, urethra
3) trachea, bronchi, lung
4) cartilage, bone
5) skeletal muscles
6) hair, nails, skin
7) blood vessels, heart
8) pituitary gland, thyroid, thymus
9) brain, spinal cord, nerves
10) thymus, lymph nodes, lymphatic vessels, spleen
11) ovary, uterus, cervix, vagina
12) prostate, testicle, penis


Exercise 7. Say what the following sciences study.

1) biology
2) zoology
3) microbiology
4) biochemistry
5) molecular biology
6) cellular biology
7) physiology
8) ecology
9) ethology
10) genetics
11) botany
12) anthropology
13) ornithology
14) ichthyology
15) mycology
16) protozoology
17) herpetology
18) entomology
19) physical anthropology


Exercise 8. Insert the missing terms.

Biology is the study of life. At the highest level is broken down based on the type of organism being studied: , the study of animals; , of plants; and , of microorganisms. Each field has contributed to mankind or the Earth’s well-being in numerous ways. Most prominently: botany, to agriculture; zoology, to livestock and protection of ecologies; and microbiology, to the study of disease and ecosystems in general.

Besides classifications based on the category of organism being studied, biology contains many other specialized sub-disciplines, which may focus on just one category of organism or address organisms from different categories. This includes , the interface between biology and chemistry; , which looks at life on the molecular level; , which studies different types of cells and how they work; , which looks at organisms at the level of tissue and organs; , which studies the interactions between organisms themselves; , which studies the behavior of animals, especially complex animals; and , overlapping with molecular biology, which studies the code of life, DNA.

Exercise 9. Answer the questions.
  1. Into what sciences is biology subdivided on the basis of the type of organism being studied?
  2. What contribution has biology made to mankind and the Earth’s well-being?
  3. What sub-disciplines does biology contain apart from zoology, botany, and microbiology?
  4. What does physiology (ethology) study?
  5. What is the subject matter of ecology?
  6. What theories lay the foundation of modern biology?
  7. What characteristics do nearly all living things share?
  8. What are the two most accepted theories of the origin of life?
  9. What is the essence of the theories of the origin of life?
  10. What are the most common elements in living things?
  11. What is the simplest chemical compound of importance to living things?
  12. What element do most of the principal compounds in living things contain?
  13. What are the four main types of macromolecules?
  14. What macromolecules serve as the principal energy source for most living things?
  15. What are the best-known lipids?
  16. What are the most complex and varied macromolecules in living things?
  17. What functions do nucleic acids perform?
Exercise 10. Translate into Russian/ Belarusian.
  1. Biology literally means "the study of life". Biology is such a broad field, covering the minute workings of chemical machines inside our cells, to broad scale concepts of ecosystems and global climate change.
  2. The foundations of modern biology include four components: cell theory; that life is made of fundamental units called cells; evolution, that life is not deliberately designed but rather evolves incrementally through random mutations and natural selection; gene theory, that tiny molecular sequences of DNA dictate the entire structure of an organism and are passed from parents to offspring; and homeostasis, that each organism’s body includes a complex suite of processes designed to preserve its biochemistry from the entropic effects of the external environment.
  3. Each field of biology has contributed to mankind or the Earth’s well-being in numerous ways. Most prominently: botany, to agriculture; zoology, to livestock and protection of ecologies; and microbiology, to the study of disease and ecosystems in general.
  4. I do not believe any concept in science has ever given rise to as many controversies and controversial debates as evolution has. But even with so many controversies, nothing in biology makes sense except in the light of evolution. When we think of evolution, the first name to strike even someone who is not from a biological sciences background would be Charles Darwin. Not a word can be written on evolution without mentioning the name of this pioneering evolutionary biologist. His work On the Origin of Species has been the topic of much discussion ever since it was first published.
  5. Systems biology is a term used to describe a number of trends in bioscience research, and a movement which draws on those trends. Proponents describe systems biology as a biology-based inter-disciplinary study field that focuses on complex interactions in biological systems, claiming that it uses a new perspective (holism instead of reduction). Particularly from year 2000 onwards, the term is used widely in the biosciences, and in a variety of contexts. An often stated ambition of systems biology is the modeling and discovery of emergent properties, properties of a system whose theoretical description is only possible using techniques which fall under the remit of systems biology. These typically involve cell signaling networks, via long-range allostery.
  6. Animal organs are usually composed of more than one cell type. Recall that the stomach contains all four animal tissue types: epithelium to line the stomach and secrete gastric juices; connective tissues to give the stomach flexibility to expand after a large meal; smooth muscle tissues to churn and digest that meal without the need for conscious thought (indeed, we are aware of that action only when we burp or suffer some sort of gastric distress!); and nervous tissues to monitor the progress of food as it is worked on by the stomach, and to direct secretion and muscle activity. Each organ typically performs a given function set. The stomach is an organ composed of tissues that aid in the mechanical and chemical breakdown of food. Most organs have functions in only one organ system. The stomach is involved only in the digestion of food as part of the digestive system. Organ systems, such as the digestive system, are collections of organs that perform a major function for the organism.
  7. Homeostasis is the maintenance of a dynamic range of conditions within which the organism can function. Temperature, pH, and energy are major components of this concept. Thermodynamics is a field of study that covers the laws governing energy transfers, and thus the basis for life on earth. Two major laws are known: the conservation of matter, and entropy. The universe is composed of two things: matter (atoms, etc.) and energy.
  8. Homeostasis is the maintenance of a stable internal environment. Homeostasis is a term coined in 1959 to describe the physical and chemical parameters that an organism must maintain to allow proper functioning of its component cells, tissues, organs, and organ systems. Enzymes function best when within a certain range of temperature and pH, and cells must strive to maintain a balance between having too much or too little water in relation to their external environment. Both situations demonstrate homeostasis. Just as we have a certain temperature range (or comfort zone), so our body has a range of environmental (internal as well as external) parameters within which it works best. Multicellular organisms accomplish this by having organs and organ systems that coordinate their homeostasis. In addition to the other functions that life must perform, unicellular creatures must accomplish their homeostasis within but a single cell!
  9. Eleven major organ systems are present within animals, although some animals lack one or more of them. The vertebrate body has two cavities: the thoracic, which contains the heart and lungs; and the abdominal, which contains digestive organs. The head, or cephalic region, contains four of the five senses as well as a brain encased in the bony skull.
  10. Eleven major organ systems are: the integumentary, skeletal, muscular, digestive, respiratory, circulatory or cardiovascular, lymphatic, nervous, endocrine, excretory, and reproductive systems.
Exercise 11. Translate into English.
  1. Биология – наука о жизни (живой природе), одна из естественных наук, предметом которой являются живые существа и их взаимодействие с окружающей средой.
  2. Биология – это комплекс знаний о жизни и совокупность научных дисциплин, изучающих живое.
  3. Биология исследует многообразие существующих и вымерших живых существ, их строение, функции, происхождение, эволюцию, распространение и индивидуальное развитие, связи друг с другом, между сообществами и с неживой природой.
  4. Биология рассматривает общие и частные закономерности, присущие жизни во всех ее проявлениях и свойствах: обмен веществ, размножение, наследственность, изменчивость, приспособляемость, рост, развитие, раздражимость, подвижность и некоторые другие.
  5. Биология изучает все аспекты жизни, в частности, структуру, функционирование, рост, происхождение, эволюцию и распределение живых организмов на Земле.
  6. Биология классифицирует и описывает живые существа, происхождение их видов, взаимодействие между собой и с окружающей средой.
  7. Биология включает в себя зоологию, ботанику, микробиологию, экологию и другие дисциплины.
Exercise 12. Translate the text using PROMT (Déjà Vu, TRADOS). Analyze the translation and make corrections.

Characteristics of Living Things

(from www.sciencelearn.org.nz)

All individuals which have life in them are known as living things. Broadly, these living things can be classified as plants and animals. They both have common characteristics as they depend on oxygen for life. These living things follow a universal circle of life with birth, reproduction and death. They need all the basic nutrients for growth and development and are prone to disturbances in their metabolism. They share a mutual bonding through the ecosystem they survive in i.e. plants depend on animals for carbon dioxide and animals depend on plants for oxygen.

The basic component present in every living thing is the cell. Both plants and animals are made up of one to countless number of cells which carry out different sets of functions. Life before evolution began from a single cell. Similarly even today, life is generated from a single cell which then divides or multiplies to give rise to a complex living form. After fertilization, once the zygote is formed, the cells start differentiating into their types and over a certain period of time give rise to a fully developed, mature living thing.

One of the most important characteristics of living things is the energy that they need to survive. Plants and animals use various forms of energy for the development of their bodies. The chemical processes that occur within a living organism in order to maintain life are called metabolism. Plants use the energy from the sun or solar energy to carry out photosynthesis which is the process for making their food (glucose). They are hence known as autotrophs. Animals and humans however cannot produce their own food and are dependent on plants and other animals for their food and hence they are called the heterotrophs. Therefore, energy is a common characteristic needed by all living things.

One of the rules of nature followed by all living things is growth. As development is an involuntary process, every cell in living things has to age. Growth and change is a part of all living organisms as cells divide to give rise to new and identical ones. Sometimes due to some genetic defects, during differentiation, some cells mutate to form other types of cells and result in complex organisms. This process of constant development and growth is also called organogenesis.

All organisms reproduce to continue their species' life. This is also one of the main characteristics of living things. Plants and animals have a reproductive system which is completely developed at puberty. There are two types of reproduction prevalent in nature, viz. sexual and asexual. The sexual reproduction involves the combination of genetic material to give rise to a single zygote that further develops into a bigger organism. The asexual reproduction involves the splitting of one organism or cell to form two separate individuals of the same species.

Every living thing is highly organized when it comes to the pattern or built of the body. Plants as well as animals have very complicated cell structures arranged very uniquely in the different organs. The cells form organelles, and organelles form organs. The organs make up the various parts of the organism. This is a network which every cell follows and thus living things are called highly organized beings. Death is also considered to be one of the most important characteristics of living things as whatever is created has to come to an end. Both plants and animals have limited life spans during which they go through their life processes like development and reproduction. As the cells age over a particular time period, these overgrown cells start becoming weak and lose their functions. They can't survive the atmospheric pressures and give in to them eventually. This is called death of the living things. They all have a particular age they live up to and then surrender to nature.

Some of the other living thing characteristics include homeostasis, which is the process to maintain stable internal conditions for survival. These conditions have to be maintained for body temperature, heartbeat, water content, etc. When the homeostasis is regulated the metabolism of the body is regulated and the living things stay healthy and fit.

Movement is also one such characteristic which is common to all living things. These movements depend on each species of plants and animals. Adaptation and defense are considered as common traits too. Every living thing has to adapt to certain conditions for survival and if it can't then it won't survive. Defense is also a gift that is given to every living thing and it is their right to protect themselves from predators.

Evolution is a type of miracle that has accompanied us for billions of years and is still in process. Eventually all living things complement each other through their characteristics and that is what Darwin's theory of evolution is all about.

Exercise 13. Write a précis and an annotation of the text given below.

Classification of Living Things and Naming

(from www.softschools.com)

With so many flora and fauna on planet Earth, there must be a method to classify each organism to distinguish it from others so it can be correctly identified. In science, the practice of classifying organisms is called taxonomy. To distinguish different levels of similarity, each classifying group, called taxon (pl. taxa) is subdivided into other groups: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species. The domain is the broadest category, while species is the most specific category available.

Binomial nomenclature is used to name an organism, where the first word beginning with a capital letter is the genus of the organism and the second word beginning with a lowercase letter is the species of the organism. The name must be in italics and in Latin, which was the major language of arts and sciences in the 18th century. The scientific name can be also abbreviated, where the genus is shortened to only its first letter followed by a period. For example: Lepus europaeus would become L. europaeus'.

There are two basic types of cells: eukaryotes and prokaryotes.

Eukaryotes are more complex in structure, with nuclei and membrane-bound organelles. Some characteristics of eukaryotes are:

  • Large (100 – 1000 μm).
  • DNA in nucleus, bounded by membrane.
  • Genome consists of several chromosomes.
  • Sexual reproduction common, by mitosis and meiosis.
  • Mitochondria and other organelles present.
  • Most forms are multicellular.
  • Aerobic.

Prokaryotes refer to the smallest and simplest type of cells, without a true nucleus and no membrane-bound organelles. Bacteria fall under this category. Some characteristics:

  • Small (1-10 μm).
  • DNA circular, unbounded.
  • Genome consists of single chromosome.
  • Asexual reproduction common, not by mitosis or meiosis.
  • No general organelles.
  • Most forms are singular.
  • Anaerobic.

The three domains (Archaea, Bacteria (Eubacteria), and Eukaryota) are organised based on the difference between eukaryotes and prokaryotes.

There are six kingdoms in taxonomy: plants, animals, protista (micro-organisms which are neither animals nor plants), fungi (mushrooms and moulds), eubacteria (monera), archaebacteria ( bacteria which live in extreme environments, have unique properties and features, their cell walls lack peptidoglycan).

One goal of taxonomy is to determine the evolutionary history of organisms. This can be achieved by comparing species living today with species in the past. The comparison in anatomy and structure is based on data from development, physical anatomy, biochemistry, DNA, behaviour, and ecological preferences.

Biochemical analysis of animals similar in appearance have yielded surprising results. For example, although guinea pigs were once considered to be rodents, like mice, biochemistry led them to be in the taxon of their own.

Modern taxonomy is based on many hypotheses' of the evolutionary history of organisms, known as phylogeny. Scientists develop a hypothesis on the history of an animal and utilise modern science and technology to prove the phylogeny.

Cladistics is a classification system which is based on phylogeny. Expanding on phylogeny, cladistics is based on the assumption that each group of related species has one common ancestor and would therefore retain some ancestral characteristics. Moreover, as these related species evolve and diverge from their common ancestor, they would develop unique characteristics. Such characteristics are known as derived characteristics.

The principles of phylogeny and cladistics can be expressed visually as a cladogram, a branching diagram which acts as a family (phylogenetic) tree for similar species. A cladogram can also be used to test alternative hypotheses for an animal's phylogeny. In order to determine the most likely cladogram, the derived characteristics of similar species are matched and analysed.

The diversity in our planet is attributed to diversity within a species. As the world changed in climate and in geography as time passed, the characteristics of species diverged so much that new species were formed. This process, by which new species evolve, was first described by British naturalist Charles Darwin as natural selection.

For an organism to change, genetic mutations must occur. At times, genetic mutations are accidental, as in the case of prokaryotes when they undergo asexual reproduction. For most eukaryotes, genetic mutations occur through sexual reproduction, where meiosis produces haploid gametes from the original parent cells. The fusion of these haploid gametes into a diploid zygote results in genetic variation in each generation. Over time, with enough arrangement of genes and traits, new species are produced. Sexual reproduction creates an immense potential of genetic variety.

One goal of taxonomy is to determine the evolutionary history of organisms. This can be achieved by comparing species living today with species in the past. The comparison in anatomy and structure is based on data from development, physical anatomy, biochemistry, DNA, behaviour, and ecological preferences.

Biochemical analysis of animals similar in appearance have yielded surprising results. For example, although guinea pigs were once considered to be rodents, like mice, biochemistry led them to be in the taxon of their own.

Modern taxonomy is based on many hypotheses' of the evolutionary history of organisms, known as phylogeny. Scientists develop a hypothesis on the history of an animal and utilise modern science and technology to prove the phylogeny.

Cladistics is a classification system which is based on phylogeny. Expanding on phylogeny, cladistics is based on the assumption that each group of related species has one common ancestor and would therefore retain some ancestral characteristics. Moreover, as these related species evolve and diverge from their common ancestor, they would develop unique characteristics. Such characteristics are known as derived characteristics.

The principles of phylogeny and cladistics can be expressed visually as a cladogram, a branching diagram which acts as a family (phylogenetic) tree for similar species. A cladogram can also be used to test alternative hypotheses for an animal's phylogeny. In order to determine the most likely cladogram, the derived characteristics of similar species are matched and analysed.

Exercise 14. Write an annotation of the text given below.

Human Body

(from www.encyclopedia.com)

The muscular system produces body movements, body heat, maintains posture, and supports the body. Muscle fibers are the main cell type. Action of this system is closely tied to that of the skeletal system, which provides support and protection, and attachment points for muscles. The skeletal system provides rigid framework for movement. It supports and protects the body and body parts, produces blood cells, and stores minerals.

The skin or integument is the outermost protective layer. It prevents water loss from and invasion of foreign microorganisms and viruses into the body. There are three layers of the skin. The epidermis is the outer, thinner layer of skin. Basal cells continually undergo mitosis. Skin is waterproof because keratin, a protein is produced. The next layer is the dermis a layer of fibrous connective tissue. Within the dermis many structures are located, such as sweat glands, hair follicles and oil glands. The subcutaneous layer is composed of loose connective tissue. Adipose tissue occurs here, serving primarily for insulation. Nerve cells run through this region, as do arteries and veins.

The respiratory system moves oxygen from the external environment into the internal environment; also removes carbon dioxide. The respiratory system exchanges gas between lungs (gills in fish) and the outside environment. It also maintains pH of the blood and facilitates exchange of carbon dioxide and oxygen.

The digestive system digests and absorbs food into nutrient molecules by chemical and mechanical breakdown; eliminates solid wastes into the environment. Digestion is accomplished by mechanical and chemical means, breaking food into particles small enough to pass into bloodstream. Absorption of food molecules occurs in the small intestine from where they are sent into circulatory system. The digestive system also recycles water and reclaims vitamins from food in the large intestine.

The circulatory or cardiovascular system transports oxygen, carbon dioxide, nutrients, waste products, immune components, and hormones. Major organs include the heart, capillaries, arteries, and veins. The lymphatic system also transports excess fluids to and from circulatory system and transports fat to the heart.

The immune (lymphatic) system defends the internal environment from invading microorganisms and viruses, as well as cancerous cell growth. The immune system provides cells that aid in protection of the body from disease via the antigen/antibody response. A variety of general responses are also part of this system.

The excretory system regulates volume of internal body fluids as well as eliminates metabolic wastes from the internal environment. The excretory system removes organic wastes from the blood, accumulating wastes as urea in the kidneys. These wastes are then removed as urine. This system is also responsible for maintaining fluid levels.

The nervous system coordinates and controls actions of internal organs and body systems. Memory, learning, and conscious thought are a few aspects of the functions of the nervous system. Maintaining autonomic functions such as heartbeat, breathing, control of involuntary muscle actions are performed by some of the parts of this system.

The endocrine system works with the nervous system to control the activity of the internal organs as well as coordinate long-range response to external stimuli. The endocrine system secretes hormones that regulate body metabolism, growth, and reproduction. These organs are not in contact with each other, although they communicate by chemical messages dumped into the circulatory system.

The reproductive system is mostly controlled by the endocrine system, and is responsible for survival and perpetuation of the species. Elements of the reproductive system produce hormones (from endocrine control) that control and aid in sexual development. Organs of this system produce gametes that combine in the female system to produce the next generation (embryo).

Exercise 15. Write a précis of the following text.

Pathways That Alter Homeostasis

(from https://en.wikipedia.org)

A variety of homeostatic mechanisms maintain the internal environment within tolerable limits. Either homeostasis is maintained through a series of control mechanisms, or the body suffers various illnesses or disease. When the cells in the body begin to malfunction, the homeostatic balance becomes disrupted. Eventually this leads to disease or cell malfunction. Disease and cellular malfunction can be caused in two basic ways: either, deficiency (cells not getting all they need) or toxicity (cells being poisoned by things they do not need). When homeostasis is interrupted in your cells, there are pathways to correct or worsen the problem. In addition to the internal control mechanisms, there are external influences based primarily on lifestyle choices and environmental exposures that influence our body's ability to maintain cellular health.

Nutrition: If your diet is lacking in a specific vitamin or mineral your cells will function poorly, possibly resulting in a disease condition. For example, a menstruating woman with inadequate dietary intake of iron will become anemic. Lack of hemoglobin, a molecule that requires iron, will result in reduced oxygen-carrying capacity. In mild cases symptoms may be vague (e.g. fatigue), but if the anaemia) is severe the body will try to compensate by increasing cardiac output, leading to palpitations and sweatiness, and possibly to heart failure.

Toxins: Any substance that interferes with cellular function, causing cellular malfunction. This is done through a variety of ways; chemical, plant, insecticides, and/or bites. A commonly seen example of this is drug overdoses. When a person takes too much of a drug their vital signs begin to waver; either increasing or decreasing, these vital signs can cause problems including coma, brain damage and even death.

Psychological: Your physical health and mental health are inseparable. Our thoughts and emotions cause chemical changes to take place either for better as with meditation, or worse as with stress.

Physical: Physical maintenance is essential for our cells and bodies. Adequate rest, sunlight, and exercise are examples of physical mechanisms for influencing homeostasis. Lack of sleep is related to a number of ailments such as irregular cardiac rhythms, fatigue, anxiety and headaches.

Genetic/Reproductive: Inheriting strengths and weaknesses can be part of our genetic makeup. Genes are sometimes turned off or on due to external factors which we can have some control over, but at other times little can be done to correct or improve genetic diseases. Beginning at the cellular level a variety of diseases come from mutated genes. For example, cancer can be genetically inherited or can be caused due to a mutation from an external source such as radiation or genes altered in a fetus when the mother uses drugs.

Medical: Because of genetic differences some bodies need help in gaining or maintaining homeostasis. Through modern medicine our bodies can be given different aids, from anti-bodies to help fight infections, or chemotherapy to kill harmful cancer cells. Traditional and alternative medical practices have many benefits, but like any medical practice the potential for harmful effects is present. Whether by nosocomial infections, or wrong dosage of medication, homeostasis can be altered by that which is trying to fix it. Trial and error with medications can cause potential harmful reactions and possibly death if not caught soon enough.

The factors listed above all have their effects at the cellular level, whether harmful or beneficial. Inadequate beneficial pathways (deficiency) will almost always result in a harmful waver in homeostasis. Too much toxicity also causes homeostatic imbalance, resulting in cellular malfunction. By removing negative health influences, and providing adequate positive health influences, your body is better able to self-regulate and self-repair, thus maintaining homeostasis.