an individual living entity is referred to as what

Chapter one: Introduction to Biology

i.1 Themes and Concepts of Biology

Past the terminate of this section, yous will exist able to:

• Identify and describe the properties of life
• Describe the levels of organization among living things
• List examples of dissimilar sub disciplines in biological science

Sentry a video about Evolution by Natural Selection.

Biology is the science that studies life. What exactly is life? This may audio like a silly question with an obvious reply, but it is not easy to define life. For case, a co-operative of biological science called virology studies viruses, which exhibit some of the characteristics of living entities but lack others. It turns out that although viruses can attack living organisms, cause diseases, and even reproduce, they do non meet the criteria that biologists utilize to define life.

From its earliest beginnings, biological science has wrestled with four questions: What are the shared properties that make something "live"? How practice those various living things function? When faced with the remarkable diverseness of life, how do nosotros organize the unlike kinds of organisms so that we tin amend understand them? And, finally—what biologists ultimately seek to understand—how did this diversity arise and how is it continuing? As new organisms are discovered every day, biologists continue to seek answers to these and other questions.

Properties of Life

All groups of living organisms share multiple key characteristics or functions: order, sensitivity or response to stimuli, reproduction, accommodation, growth and development, regulation, homeostasis, and energy processing. When viewed together, these eight characteristics serve to ascertain life.

Order

Organisms are highly organized structures that consist of one or more cells. Even very uncomplicated, single-celled organisms are remarkably complex. Within each cell, atoms brand upwards molecules. These in turn make up cell components or organelles. Multicellular organisms, which may consist of millions of individual cells, have an reward over unmarried-celled organisms in that their cells can exist specialized to perform specific functions, and even sacrificed in sure situations for the good of the organism as a whole. How these specialized cells come together to form organs such as the heart, lung, or skin in organisms like the toad shown in Figure i. 2 will exist discussed later.

Figure ane.ii A toad represents a highly organized construction consisting of cells, tissues, organs, and organ systems.

Sensitivity or Response to Stimuli

Organisms respond to various stimuli. For example, plants can bend toward a source of calorie-free or respond to impact. Fifty-fifty tiny leaner tin move toward or away from chemicals (a procedure called chemotaxis) or light (phototaxis). Movement toward a stimulus is considered a positive response, while motion away from a stimulus is considered a negative response.

 

Figure 1.3 The leaves of this sensitive institute (Mimosa pudica) will instantly droop and fold when touched. Afterwards a few minutes, the plant returns to its normal state.

Concept in Action

Sentinel this video to see how the sensitive constitute responds to a touch stimulus.

Reproduction

Single-celled organisms reproduce by starting time duplicating their DNA, which is the genetic material, and then dividing it every bit as the prison cell prepares to split to form two new cells. Many multicellular organisms (those made upwards of more than i prison cell) produce specialized reproductive cells that will course new individuals. When reproduction occurs, Dna containing genes is passed along to an organism's offspring. These genes are the reason that the offspring will belong to the same species and volition take characteristics similar to the parent, such every bit fur color and claret blazon.

Accommodation

All living organisms showroom a "fit" to their environment. Biologists refer to this fit as accommodation and it is a consequence of evolution by natural selection, which operates in every lineage of reproducing organisms. Examples of adaptations are various and unique, from heat-resistant Archaea that live in boiling hot springs to the natural language length of a nectar-feeding moth that matches the size of the flower from which it feeds. All adaptations raise the reproductive potential of the individual exhibiting them, including their ability to survive to reproduce. Adaptations are non constant. As an environment changes, natural selection causes the characteristics of the individuals in a population to track those changes.

Growth and Development

Organisms grow and develop according to specific instructions coded for past their genes. These genes provide instructions that will direct cellular growth and development, ensuring that a species' young volition abound upward to showroom many of the same characteristics as its parents.

Figure 1.4 Although no ii wait alike, these kittens have inherited genes from both parents and share many of the same characteristics.

Regulation

Even the smallest organisms are circuitous and require multiple regulatory mechanisms to coordinate internal functions, such as the transport of nutrients, response to stimuli, and coping with environmental stresses. For instance, organ systems such equally the digestive or circulatory systems perform specific functions like carrying oxygen throughout the body, removing wastes, delivering nutrients to every cell, and cooling the body.

Homeostasis

To function properly, cells require appropriate weather condition such as proper temperature, pH, and concentrations of diverse chemicals. These conditions may, however, change from one moment to the next. Organisms are able to maintain internal conditions within a narrow range well-nigh constantly, despite environmental changes, through a process called homeostasis or "steady state"—the ability of an organism to maintain constant internal weather. For example, many organisms regulate their body temperature in a process known as thermoregulation. Organisms that live in common cold climates, such as the polar bear, accept body structures that assist them withstand low temperatures and conserve body heat. In hot climates, organisms have methods (such as perspiration in humans or panting in dogs) that aid them to shed excess body heat.

Figure 1.5 Polar bears and other mammals living in ice-covered regions maintain their body temperature by generating heat and reducing heat loss through thick fur and a dense layer of fat under their skin.

Energy Processing

All organisms (such as the California condor shown in Figure 1.vi) utilise a source of energy for their metabolic activities. Some organisms capture free energy from the sun and convert it into chemical energy in nutrient; others use chemical free energy from molecules they take in.

Figure 1.6 A lot of energy is required for a California condor to fly. Chemical energy derived from food is used to ability flight. California condors are an endangered species; scientists have strived to place a wing tag on each bird to help them identify and locate each private bird.

Levels of Organization of Living Things

Living things are highly organized and structured, following a hierarchy on a scale from small to big. The atom is the smallest and almost cardinal unit of measurement of matter. Information technology consists of a nucleus surrounded past electrons. Atoms grade molecules. A molecule is a chemical structure consisting of at least two atoms held together by a chemical bond. Many molecules that are biologically important are macromolecules, large molecules that are typically formed by combining smaller units chosen monomers. An example of a macromolecule is deoxyribonucleic acid (Deoxyribonucleic acid), which contains the instructions for the performance of the organism that contains it.

Figure ane.7 A molecule, like this big Deoxyribonucleic acid molecule, is equanimous of atoms.

Concept in Action

To see an animation of this DNA molecule, click here.

Some cells contain aggregates of macromolecules surrounded by membranes; these are called organelles. Organelles are modest structures that be within cells and perform specialized functions. All living things are fabricated of cells; the cell itself is the smallest central unit of structure and office in living organisms. (This requirement is why viruses are not considered living: they are not made of cells. To make new viruses, they have to invade and hijack a living cell; only and then can they obtain the materials they need to reproduce.) Some organisms consist of a single cell and others are multicellular. Cells are classified every bit prokaryotic or eukaryotic. Prokaryotes are single-celled organisms that lack organelles surrounded past a membrane and do not have nuclei surrounded past nuclear membranes; in dissimilarity, the cells of eukaryotes do have membrane-spring organelles and nuclei.

In most multicellular organisms, cells combine to make tissues, which are groups of similar cells conveying out the same function. Organs are collections of tissues grouped together based on a common office. Organs are present non only in animals but also in plants. An organ system is a higher level of system that consists of functionally related organs. For example vertebrate animals have many organ systems, such as the circulatory system that transports blood throughout the body and to and from the lungs; it includes organs such as the center and claret vessels. Organisms are individual living entities. For example, each tree in a forest is an organism. Single-celled prokaryotes and single-celled eukaryotes are too considered organisms and are typically referred to every bit microorganisms.

Figure ane.8 From an atom to the entire Earth, biological science examines all aspects of life.

Which of the following statements is false?

1. Tissues exist within organs which exist within organ systems.
2. Communities be inside populations which be within ecosystems.
3. Organelles exist inside cells which exist within tissues.
4. Communities exist within ecosystems which exist in the biosphere.

All the individuals of a species living within a specific surface area are collectively called a population. For example, a forest may include many white pino copse. All of these pine copse represent the population of white pine trees in this woods. Unlike populations may live in the aforementioned specific area. For case, the forest with the pine trees includes populations of flowering plants and also insects and microbial populations. A community is the set of populations inhabiting a particular surface area. For example, all of the copse, flowers, insects, and other populations in a forest form the wood'due south community. The forest itself is an ecosystem. An ecosystem consists of all the living things in a particular area together with the abiotic, or not-living, parts of that environment such as nitrogen in the soil or rainwater. At the highest level of organization, the biosphere is the collection of all ecosystems, and information technology represents the zones of life on World. It includes land, water, and portions of the atmosphere.

The Diversity of Life

The science of biological science is very broad in scope because there is a tremendous diversity of life on Earth. The source of this diversity is evolution, the process of gradual change during which new species ascend from older species. Evolutionary biologists study the evolution of living things in everything from the microscopic globe to ecosystems.

In the 18th century, a scientist named Carl Linnaeus get-go proposed organizing the known species of organisms into a hierarchical taxonomy. In this system, species that are about like to each other are put together inside a grouping known as a genus. Furthermore, similar genera (the plural of genus) are put together inside a family. This grouping continues until all organisms are collected together into groups at the highest level. The electric current taxonomic arrangement now has 8 levels in its hierarchy, from lowest to highest, they are: species, genus, family unit, guild, class, phylum, kingdom, and domain. Thus species are grouped within genera, genera are grouped inside families, families are grouped within orders, and so on.

Figure one.9 This diagram shows the levels of taxonomic hierarchy for a domestic dog, from the broadest category—domain—to the most specific—species.

The highest level, domain, is a relatively new addition to the organization since the 1990s. Scientists now recognize three domains of life, the Eukarya, the Archaea, and the Bacteria. The domain Eukarya contains organisms that have cells with nuclei. It includes the kingdoms of fungi, plants, animals, and several kingdoms of protists. The Archaea, are unmarried-celled organisms without nuclei and include many extremophiles that live in harsh environments similar hot springs. The Bacteria are some other quite unlike grouping of unmarried-celled organisms without nuclei. Both the Archaea and the Bacteria are prokaryotes, an breezy name for cells without nuclei. The recognition in the 1990s that certain "bacteria," now known as the Archaea, were as different genetically and biochemically from other bacterial cells equally they were from eukaryotes, motivated the recommendation to divide life into three domains. This dramatic modify in our knowledge of the tree of life demonstrates that classifications are non permanent and will change when new information becomes available.

In improver to the hierarchical taxonomic system, Linnaeus was the beginning to proper name organisms using two unique names, at present called the binomial naming arrangement. Earlier Linnaeus, the use of common names to refer to organisms acquired confusion because there were regional differences in these common names. Binomial names consist of the genus proper noun (which is capitalized) and the species proper name (all lower-case). Both names are set up in italics when they are printed. Every species is given a unique binomial which is recognized the globe over, so that a scientist in any location tin know which organism is being referred to. For example, the Due north American blue jay is known uniquely as Cyanocitta cristata. Our ain species is Homo sapiens.

Figure i.10 These images stand for different domains. The scanning electron micrograph shows (a) bacterial cells vest to the domain Bacteria, while the (b) extremophiles, seen all together as colored mats in this hot spring, vest to domain Archaea. Both the (c) sunflower and (d) king of beasts are part of domain Eukarya.

Evolution in Action

Carl Woese and the Phylogenetic Tree

The evolutionary relationships of various life forms on World tin be summarized in a phylogenetic tree. A phylogenetic tree is a diagram showing the evolutionary relationships among biological species based on similarities and differences in genetic or physical traits or both. A phylogenetic tree is composed of branch points, or nodes, and branches. The internal nodes represent ancestors and are points in evolution when, based on scientific prove, an antecedent is thought to have diverged to form ii new species. The length of each branch can be considered every bit estimates of relative time.

In the past, biologists grouped living organisms into five kingdoms: animals, plants, fungi, protists, and leaner. The pioneering work of American microbiologist Carl Woese in the early on 1970s has shown, nevertheless, that life on Earth has evolved along three lineages, at present chosen domains—Bacteria, Archaea, and Eukarya. Woese proposed the domain every bit a new taxonomic level and Archaea as a new domain, to reflect the new phylogenetic tree. Many organisms belonging to the Archaea domain alive nether farthermost conditions and are called extremophiles. To construct his tree, Woese used genetic relationships rather than similarities based on morphology (shape). Diverse genes were used in phylogenetic studies. Woese's tree was constructed from comparative sequencing of the genes that are universally distributed, institute in some slightly altered form in every organism, conserved (meaning that these genes take remained simply slightly changed throughout evolution), and of an appropriate length.

Figure 1.11 This phylogenetic tree was constructed by microbiologist Carl Woese using genetic relationships. The tree shows the separation of living organisms into three domains: Bacteria, Archaea, and Eukarya. Bacteria and Archaea are organisms without a nucleus or other organelles surrounded by a membrane and, therefore, are prokaryotes.

Branches of Biological Study

Spotter a video near Scientific discipline and Medicine

The scope of biological science is wide and therefore contains many branches and sub disciplines. Biologists may pursue 1 of those sub disciplines and piece of work in a more than focused field. For instance, molecular biology studies biological processes at the molecular level, including interactions amongst molecules such as DNA, RNA, and proteins, as well as the manner they are regulated. Microbiology is the study of the structure and function of microorganisms. It is quite a broad branch itself, and depending on the subject of study, there are as well microbial physiologists, ecologists, and geneticists, among others.

Another field of biological report, neurobiology, studies the biological science of the nervous arrangement, and although it is considered a branch of biology, it is likewise recognized equally an interdisciplinary subject field known as neuroscience. Considering of its interdisciplinary nature, this sub discipline studies different functions of the nervous system using molecular, cellular, developmental, medical, and computational approaches.

Figure 1.12 Researchers work on excavating dinosaur fossils at a site in Castellón, Espana.

Paleontology, another branch of biology, uses fossils to study life'south history. Zoology and botany are the study of animals and plants, respectively. Biologists can also specialize as biotechnologists, ecologists, or physiologists, to proper noun simply a few areas. Biotechnologists use the knowledge of biological science to create useful products. Ecologists study the interactions of organisms in their environments. Physiologists report the workings of cells, tissues and organs. This is simply a modest sample of the many fields that biologists can pursue. From our own bodies to the world we live in, discoveries in biological science can touch on u.s. in very direct and important ways. We depend on these discoveries for our health, our food sources, and the benefits provided past our ecosystem. Considering of this, knowledge of biology can benefit us in making decisions in our twenty-four hours-to-mean solar day lives.

The development of technology in the twentieth century that continues today, particularly the applied science to depict and manipulate the genetic cloth, DNA, has transformed biology. This transformation will allow biologists to keep to understand the history of life in greater detail, how the human being trunk works, our human origins, and how humans can survive as a species on this planet despite the stresses caused past our increasing numbers. Biologists keep to decipher huge mysteries about life suggesting that we take only begun to understand life on the planet, its history, and our relationship to information technology. For this and other reasons, the knowledge of biological science gained through this textbook and other printed and electronic media should be a do good in whichever field you enter.

Forensic Scientist

Forensic science is the application of science to answer questions related to the law. Biologists as well as chemists and biochemists can be forensic scientists. Forensic scientists provide scientific prove for utilise in courts, and their task involves examining trace material associated with crimes. Interest in forensic science has increased in the final few years, possibly because of pop television shows that characteristic forensic scientists on the chore. Also, the development of molecular techniques and the establishment of Deoxyribonucleic acid databases take updated the types of piece of work that forensic scientists can do. Their job activities are primarily related to crimes against people such as murder, rape, and assault. Their work involves analyzing samples such as hair, claret, and other body fluids and too processing Deoxyribonucleic acid establish in many unlike environments and materials. Forensic scientists also analyze other biological evidence left at crime scenes, such every bit insect parts or pollen grains. Students who want to pursue careers in forensic scientific discipline will most likely be required to take chemistry and biology courses also as some intensive math courses.

Figure i.13 This forensic scientist works in a Deoxyribonucleic acid extraction room at the U.S. Army Criminal Investigation Laboratory.

Department Summary

Biological science is the science of life. All living organisms share several key properties such equally club, sensitivity or response to stimuli, reproduction, adaptation, growth and development, regulation, homeostasis, and energy processing. Living things are highly organized following a bureaucracy that includes atoms, molecules, organelles, cells, tissues, organs, and organ systems. Organisms, in turn, are grouped as populations, communities, ecosystems, and the biosphere. Evolution is the source of the tremendous biological diversity on Globe today. A diagram called a phylogenetic tree can be used to show evolutionary relationships among organisms. Biology is very wide and includes many branches and sub disciplines. Examples include molecular biology, microbiology, neurobiology, zoology, and botany, amongst others.

cantlet: a bones unit of thing that cannot exist broken down by normal chemical reactions

biology: the study of living organisms and their interactions with one some other and their environments

biosphere: a drove of all ecosystems on Earth

cell: the smallest key unit of structure and function in living things

community: a prepare of populations inhabiting a particular area

ecosystem: all living things in a particular area together with the abiotic, nonliving parts of that environment

eukaryote: an organism with cells that have nuclei and membrane-bound organelles

development: the process of gradual change in a population that tin can too lead to new species arising from older species

homeostasis: the power of an organism to maintain constant internal conditions

macromolecule: a large molecule typically formed past the joining of smaller molecules

molecule: a chemical structure consisting of at to the lowest degree 2 atoms held together by a chemical bond

organ: a structure formed of tissues operating together to perform a common function

organ system: the college level of organization that consists of functionally related organs

organelle: a membrane-leap compartment or sac within a cell

organism: an individual living entity

phylogenetic tree: a diagram showing the evolutionary relationships amid biological species based on similarities and differences in genetic or physical traits or both

population: all individuals within a species living within a specific area

prokaryote: a unicellular organism that lacks a nucleus or whatsoever other membrane-bound organelle

tissue: a group of similar cells carrying out the aforementioned part

Media Attribution

• Figure 1.two by Ivengo(RUS) © Public Domain
• Figure 1.3 past Alex Lomas © CC Past (Attribution)
• Figure 1.4 by Pieter & Renée Lanser © CC BY (Attribution)
• Figure 1.five past David © CC BY (Attribution)
• Figure 1.vi by Pacific Southwest Region USFWS © CC By (Attribution)
• Figure 1.vii past Brian0918 © Public Domain
• Figure ane.8
  • "molecule": modification of piece of work by Jane Whitney;
  • "organelles": modification of piece of work by Louisa Howard;
  • "cells": modification of work by Bruce Wetzel, Harry Schaefer, National Cancer Establish;
  • "tissue": modification of work past "Kilbad" © Public Domain
  • "organs": modification of piece of work past Mariana Ruiz Villareal, Joaquim Alves Gaspar;
  • "organisms": modification of work past Peter Dutton;
  • "ecosystem": modification of work by "gigi4791″ © CC Past (Attribution)
  • "biosphere": modification of work by NASA © Public Domain
• Figure 1.x
  • EscherichiaColi NIAID: modification of work by Rocky Mountain Laboratories, NIAID, NIH © Public Domain
  • Extremophiles modification of work past Steve Jurvetson © CC BY (Attribution)
  • Sunflower modification of work by Michael Arrighi
  • Lion modification of work by Frank Vassen  © CC By (Attribution)
• Figure i.12 past Mario Modesto © Public Domain
• Figure i.13 by U.South. Army CID Command Public Affairs

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