1.2: Mandhari na Dhana za Biolojia

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Ujuzi wa Kuendeleza

Kutambua na kuelezea mali ya maisha
Eleza viwango vya shirika kati ya vitu vilivyo hai
Kutambua na kutafsiri mti wa phylogenetic
Orodha ya mifano ya taaluma ndogo tofauti katika biolojia

Biolojia ni sayansi inayochunguza maisha, lakini ni nini hasa maisha? Hii inaweza kuonekana kama swali la silly na majibu ya wazi, lakini si rahisi kila wakati kufafanua maisha. Kwa mfano, tawi la biolojia linaloitwa virology linasoma virusi, ambalo linaonyesha baadhi ya sifa za vyombo hai lakini hukosa wengine. Inageuka kuwa ingawa virusi vinaweza kushambulia viumbe hai, kusababisha magonjwa, na hata kuzaliana, hazifikiri vigezo ambavyo wanabiolojia hutumia kufafanua maisha. Kwa hiyo, virologists si biologists, madhubuti kusema. Vilevile, baadhi ya wanabiolojia wanasoma mageuzi ya awali ya Masi yaliyotoa kupanda kwa uhai; kwa kuwa matukio yaliyotangulia maisha si matukio ya kibiolojia, wanasayansi hawa pia wametengwa na biolojia kwa maana kali ya neno hilo.

Kutoka mwanzo wake wa mwanzo, biolojia ina wrestled na maswali matatu: Ni mali ya pamoja kwamba kufanya kitu “hai” nini? Na mara tu tunajua kitu kilicho hai, tunawezaje kupata viwango vya maana vya shirika katika muundo wake? Na, hatimaye, wakati wanakabiliwa na tofauti ya ajabu ya maisha, tunawezaje kuandaa aina mbalimbali za viumbe ili tuweze kuzielewa vizuri? Kama viumbe vipya vinavyogunduliwa kila siku, wanabiolojia wanaendelea kutafuta majibu ya maswali haya na mengine.

Mali ya Maisha

Viumbe hai vyote hushiriki sifa kadhaa muhimu au kazi: utaratibu, unyeti au kukabiliana na mazingira, uzazi, kukabiliana na hali, ukuaji na maendeleo, udhibiti, homeostasis, usindikaji wa nishati, na mageuzi. Inapotazamwa pamoja, sifa hizi tisa hutumikia kufafanua maisha.

Order

Viumbe vinapangwa sana, miundo iliyoratibiwa ambayo inajumuisha seli moja au zaidi. Hata rahisi sana, viumbe vya seli moja ni ngumu sana: ndani ya kila seli, atomi hufanya molekuli; hizi pia hufanya organelles za seli na inclusions nyingine za mkononi. Katika viumbe vingi (Kielelezo\(\PageIndex{1}\)), seli zinazofanana huunda tishu. Tishu, kwa upande wake, hushirikiana kuunda viungo (miundo ya mwili yenye kazi tofauti). Viungo vinafanya kazi pamoja ili kuunda mifumo ya chombo.

Picha inaonyesha kitambaa cha rangi nyekundu kilichofunikwa kwenye matangazo ya kijani. — Kielelezo\(\PageIndex{1}\): kitambaa kinawakilisha muundo ulioandaliwa sana unao na seli, tishu, viungo, na mifumo ya chombo. (mikopo: “Ivengo” /Wikimedia Commons)

Sensitivity au Response kwa

Viumbe hujibu kwa msukumo tofauti. Kwa mfano, mimea inaweza kuinama kuelekea chanzo cha mwanga, kupanda juu ya ua na kuta, au kujibu kugusa (Kielelezo\(\PageIndex{2}\)). Hata bakteria vidogo vinaweza kusonga kuelekea au mbali na kemikali (mchakato unaoitwa chemotaxis) au mwanga (phototaxis). Movement kuelekea kichocheo inachukuliwa kuwa majibu mazuri, wakati harakati mbali na kichocheo inachukuliwa kuwa jibu hasi.

Picha ya pudica ya Mimosa inaonyesha mmea wenye majani mengi madogo yanayounganishwa na shina la kati. Nne ya shina hizi kuungana pamoja. — Kielelezo\(\PageIndex{2}\): Majani ya mmea huu nyeti (*Mimosa pudica*) yatapungua mara moja na kukunja wakati unaguswa. Baada ya dakika chache, mmea unarudi kwa kawaida. (mikopo: Alex Lomas)

Unganisha na Kujifunza

Video: Tazama video hii ili uone jinsi mimea inavyoitikia kichocheo - kuanzia kufunguliwa kwa mwanga, hadi kuifunga tendril kuzunguka tawi, na kukamata mawindo.

Uzazi

Viumbe vya seli moja huzaa kwa mara ya kwanza kurudia DNA yao, halafu kuigawanya sawasawa kadiri seli huandaa kugawa ili kuunda seli mbili mpya. Viumbe vingi vya seli mara nyingi huzalisha seli maalumu za uzazi za uzazi ambazo zitaunda watu wapya. Wakati uzazi hutokea, jeni zenye DNA hupitishwa pamoja na watoto wa kiumbe. Jeni hizi zinahakikisha kwamba watoto watakuwa wa aina moja na watakuwa na sifa zinazofanana, kama ukubwa na umbo.

Ukuaji na Maendeleo

Viumbe hukua na kuendeleza kufuatia maagizo maalum yanayosimbwa kwa jeni zao. Jeni hizi hutoa maelekezo ambayo yataongoza ukuaji wa seli na maendeleo, kuhakikisha kwamba vijana wa aina (Kielelezo\(\PageIndex{3}\)) itakua ili kuonyesha sifa nyingi sawa na wazazi wake.

Picha inaonyesha paka mama uuguzi kittens tatu: moja ina machungwa na nyeupe tabby kanzu, mwingine ni nyeusi na mguu nyeupe, wakati wa tatu ina nyeusi na nyeupe tabby kanzu. — Kielelezo\(\PageIndex{3}\): Ingawa hakuna mbili zinazoonekana sawa, kittens hizi zimerithi jeni kutoka kwa wazazi wote wawili na kushiriki sifa nyingi sawa. (mikopo: Rocky Mountain Feline Uokoaji)

Taratibu

Hata viumbe vidogo ni ngumu na vinahitaji taratibu nyingi za udhibiti ili kuratibu kazi za ndani, kujibu msisitizo, na kukabiliana na matatizo ya mazingira. Mifano miwili ya kazi za ndani zilizowekwa katika viumbe ni usafiri wa virutubisho na mtiririko wa damu. Viungo (vikundi vya tishu vinavyofanya kazi pamoja) hufanya kazi maalum, kama vile kubeba oksijeni katika mwili wote, kuondoa taka, kutoa virutubisho kwa kila seli, na kuimarisha mwili.

Homeostasis

Ili kufanya kazi vizuri, seli zinahitaji kuwa na hali zinazofaa kama vile joto sahihi, pH, na mkusanyiko sahihi wa kemikali mbalimbali. Hali hizi zinaweza, hata hivyo, kubadilika kutoka wakati mmoja hadi ujao. Viumbe vinaweza kudumisha hali ya ndani ndani ya aina nyembamba karibu daima, licha ya mabadiliko ya mazingira, kupitia homeostasis (literally, “hali thabiti”) -uwezo wa kiumbe kudumisha hali ya ndani ya mara kwa mara. Kwa mfano, kiumbe kinahitaji kudhibiti joto la mwili kupitia mchakato unaojulikana kama thermoregulation. Viumbe vinavyoishi katika hali ya hewa ya baridi, kama vile kubeba polar (Kielelezo\(\PageIndex{4}\)), vina miundo ya mwili inayowasaidia kuhimili joto la chini na kuhifadhi joto la mwili. Miundo ambayo inasaidia katika aina hii ya insulation ni pamoja na manyoya, manyoya, blubber, na mafuta. Katika hali ya hewa ya joto, viumbe vina mbinu (kama vile jasho kwa binadamu au kupiga mbwa) zinazowasaidia kumwaga joto la mwili kupita kiasi.

Picha inaonyesha kubeba nyeupe, furry polar. — Kielelezo\(\PageIndex{4}\): Polar huzaa (*Ursus maritimus*) na wanyama wengine wanaoishi katika mikoa iliyofunikwa na barafu huhifadhi joto la mwili wao kwa kuzalisha joto na kupunguza kupoteza joto kwa njia ya manyoya nene na safu nyembamba ya mafuta chini ya ngozi yao. (mikopo: “longhorndave” /Flickr)

Nishati Usindikaji

Viumbe vyote hutumia chanzo cha nishati kwa shughuli zao za kimetaboliki. Baadhi ya viumbe hukamata nishati kutoka jua na kuibadilisha kuwa nishati ya kemikali katika chakula; wengine hutumia nishati ya kemikali katika molekuli wanazozichukua kama chakula (Kielelezo\(\PageIndex{5}\)).

Picha inaonyesha condor California katika ndege na tag juu ya mrengo wake. — Kielelezo\(\PageIndex{5}\): California condor (*Gymnogyps californianus*) inatumia nishati ya kemikali inayotokana na chakula kwa nguvu ndege. Condors za California ni spishi zilizohatarishwa; ndege hii ina tag ya mrengo inayosaidia wanabiolojia kumtambua mtu binafsi. (mikopo: Pacific Southwest Region Marekani Samaki na Wanyamapori

Ngazi za Shirika la Mambo ya Kuishi

Mambo yaliyo hai yanapangwa sana na muundo, kufuatia uongozi ambao unaweza kuchunguzwa kwa kiwango kutoka ndogo hadi kubwa. Atomu ni kitengo kidogo na cha msingi zaidi cha suala. Lina kiini kilichozungukwa na elektroni. Atomi huunda molekuli. Molekuli ni muundo wa kemikali yenye angalau atomi mbili zilizoshikiliwa pamoja na vifungo kimoja au zaidi vya kemikali. Molekuli nyingi ambazo ni muhimu kibiolojia ni macromolecules, molekuli kubwa ambazo kwa kawaida hutengenezwa na upolimishaji (polymer ni molekuli kubwa inayofanywa kwa kuchanganya vitengo vidogo vinavyoitwa monoma, ambazo ni rahisi kuliko macromolecules). Mfano wa macromolecule ni asidi deoxyribonucleic (DNA) (Kielelezo\(\PageIndex{6}\)), ambayo ina maelekezo ya muundo na utendaji wa viumbe vyote vilivyo hai.

Mfano wa molekuli unaonyesha molekuli ya DNA, kuonyesha muundo wake wa helix mara mbili. — Kielelezo\(\PageIndex{6}\): Molekuli zote, ikiwa ni pamoja na molekuli hii ya DNA, zinajumuisha atomi. (mikopo: “brian0918” /Wikimedia Commons)

Unganisha na Kujifunza

Video: Watch video hii kwamba animates muundo tatu-dimensional ya molekuli DNA inavyoonekana katika Kielelezo\(\PageIndex{6}\).

Some cells contain aggregates of macromolecules surrounded by membranes; these are called organelles. Organelles are small structures that exist within cells. Examples of organelles include mitochondria and chloroplasts, which carry out indispensable functions: mitochondria produce energy to power the cell, while chloroplasts enable green plants to utilize the energy in sunlight to make sugars. All living things are made of cells; the cell itself is the smallest fundamental unit of structure and function 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 the reproductive mechanism of a living cell; only then can they obtain the materials they need to reproduce.) Some organisms consist of a single cell and others are multicellular. Cells are classified as prokaryotic or eukaryotic. Prokaryotes are single-celled or colonial organisms that do not have membrane-bound nuclei; in contrast, the cells of eukaryotes do have membrane-bound organelles and a membrane-bound nucleus.

In larger organisms, cells combine to make tissues, which are groups of similar cells carrying out similar or related functions. Organs are collections of tissues grouped together performing a common function. Organs are present not only in animals but also in plants. An organ system is a higher level of organization that consists of functionally related organs. Mammals have many organ systems. For instance, the circulatory system transports blood through the body and to and from the lungs; it includes organs such as the heart and blood vessels. Organisms are individual living entities. For example, each tree in a forest is an organism. Single-celled prokaryotes and single-celled eukaryotes are also considered organisms and are typically referred to as microorganisms.

All the individuals of a species living within a specific area are collectively called a population. For example, a forest may include many pine trees. All of these pine trees represent the population of pine trees in this forest. Different populations may live in the same specific area. For example, the forest with the pine trees includes populations of flowering plants and also insects and microbial populations. A community is the sum of populations inhabiting a particular area. For instance, all of the trees, flowers, insects, and other populations in a forest form the forest’s community. The forest itself is an ecosystem. An ecosystem consists of all the living things in a particular area together with the abiotic, non-living parts of that environment such as nitrogen in the soil or rain water. At the highest level of organization (Figure \(\PageIndex{7}\)), the biosphere is the collection of all ecosystems, and it represents the zones of life on earth. It includes land, water, and even the atmosphere to a certain extent.

Art Connection

A flow chart shows the hierarchy of living organisms. From smallest to largest, this hierarchy includes: (1) Organelles, such as nuclei, that exist inside cells. (2) Cells, such as a red blood cell. (3) Tissues, such as human skin tissue. (4) Organs such as the stomach make up the human digestive system, an example of an organ system. (5) Organisms, populations, and communities. In a forest, each pine tree is an organism. Together, all the pine trees make up a population. All the plant and animal species in the forest comprise a community. (6) Ecosystems: the coastal ecosystem in the Southeastern United States includes living organisms and the environment in which they live. (7) The biosphere: encompasses all the ecosystems on Earth. — Figure \(\PageIndex{7}\): The biological levels of organization of living things are shown. From a single organelle to the entire biosphere, living organisms are parts of a highly structured hierarchy. (credit “organelles”: modification of work by Umberto Salvagnin; credit “cells”: modification of work by Bruce Wetzel, Harry Schaefer/ National Cancer Institute; credit “tissues”: modification of work by Kilbad; Fama Clamosa; Mikael Häggström; credit “organs”: modification of work by Mariana Ruiz Villareal; credit “organisms”: modification of work by "Crystal"/Flickr; credit “ecosystems”: modification of work by US Fish and Wildlife Service Headquarters; credit “biosphere”: modification of work by NASA)

Which of the following statements is false?

Tissues exist within organs which exist within organ systems.
Communities exist within populations which exist within ecosystems.
Organelles exist within cells which exist within tissues.
Communities exist within ecosystems which exist in the biosphere.

The Diversity of Life

The fact that biology, as a science, has such a broad scope has to do with the tremendous diversity of life on earth. The source of this diversity is evolution, the process of gradual change during which new species arise from older species. Evolutionary biologists study the evolution of living things in everything from the microscopic world to ecosystems.

The evolution of various life forms on Earth can be summarized in a phylogenetic tree (Figure \(\PageIndex{8}\)). 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 nodes and branches. The internal nodes represent ancestors and are points in evolution when, based on scientific evidence, an ancestor is thought to have diverged to form two new species. The length of each branch is proportional to the time elapsed since the split.

This phylogenetic tree shows that the three domains of life, bacteria, archaea and eukarya, all arose from a common ancestor. — Figure \(\PageIndex{8}\): This phylogenetic tree was constructed by microbiologist Carl Woese using data obtained from sequencing ribosomal RNA genes. The tree shows the separation of living organisms into three domains: Bacteria, Archaea, and Eukarya. Bacteria and Archaea are prokaryotes, single-celled organisms lacking intracellular organelles. (credit: Eric Gaba; NASA Astrobiology Institute)

Evolution Connection: Carl Woese and the Phylogenetic Tree

In the past, biologists grouped living organisms into five kingdoms: animals, plants, fungi, protists, and bacteria. The organizational scheme was based mainly on physical features, as opposed to physiology, biochemistry, or molecular biology, all of which are used by modern systematics. The pioneering work of American microbiologist Carl Woese in the early 1970s has shown, however, that life on Earth has evolved along three lineages, now called domains—Bacteria, Archaea, and Eukarya. The first two are prokaryotic cells with microbes that lack membrane-enclosed nuclei and organelles. The third domain contains the eukaryotes and includes unicellular microorganisms together with the four original kingdoms (excluding bacteria). Woese defined Archaea as a new domain, and this resulted in a new taxonomic tree (Figure \(\PageIndex{8}\)). Many organisms belonging to the Archaea domain live under extreme conditions and are called extremophiles. To construct his tree, Woese used genetic relationships rather than similarities based on morphology (shape).

Woese’s tree was constructed from comparative sequencing of the genes that are universally distributed, present in every organism, and conserved (meaning that these genes have remained essentially unchanged throughout evolution). Woese’s approach was revolutionary because comparisons of physical features are insufficient to differentiate between the prokaryotes that appear fairly similar in spite of their tremendous biochemical diversity and genetic variability (Figure \(\PageIndex{9}\)). The comparison of homologous DNA and RNA sequences provided Woese with a sensitive device that revealed the extensive variability of prokaryotes, and which justified the separation of the prokaryotes into two domains: bacteria and archaea.

Photos depict: A: bacterial cells. B: a natural hot vent. C: a sunflower. D: a lion. — Figure \(\PageIndex{9}\): These images represent different domains. The (a) bacteria in this micrograph belong to Domain Bacteria, while the (b) extremophiles (not visible) living in this hot vent belong to Domain Archaea. Both the (c) sunflower and (d) lion are part of Domain Eukarya. (credit a: modification of work by Drew March; credit b: modification of work by Steve Jurvetson; credit c: modification of work by Michael Arrighi; credit d: modification of work by Leszek Leszcynski)

Branches of Biological Study

The scope of biology is broad and therefore contains many branches and subdisciplines. Biologists may pursue one of those subdisciplines and work in a more focused field. For instance, molecular biology and biochemistry study biological processes at the molecular and chemical level, including interactions among molecules such as DNA, RNA, and proteins, as well as the way they are regulated. Microbiology, the study of microorganisms, is the study of the structure and function of single-celled organisms. It is quite a broad branch itself, and depending on the subject of study, there are also microbial physiologists, ecologists, and geneticists, among others.

Career Connection: 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 evidence for use in courts, and their job involves examining trace materials associated with crimes. Interest in forensic science has increased in the last few years, possibly because of popular television shows that feature forensic scientists on the job. Also, the development of molecular techniques and the establishment of DNA databases have expanded the types 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, blood, and other body fluids and also processing DNA (Figure \(\PageIndex{10}\)) found in many different environments and materials. Forensic scientists also analyze other biological evidence left at crime scenes, such as insect larvae or pollen grains. Students who want to pursue careers in forensic science will most likely be required to take chemistry and biology courses as well as some intensive math courses.

Photo depicts a scientist working in the lab. — Figure \(\PageIndex{10}\): This forensic scientist works in a DNA extraction room at the U.S. Army Criminal Investigation Laboratory at Fort Gillem, GA. (credit: United States Army CID Command Public Affairs)

Another field of biological study, neurobiology, studies the biology of the nervous system, and although it is considered a branch of biology, it is also recognized as an interdisciplinary field of study known as neuroscience. Because of its interdisciplinary nature, this subdiscipline studies different functions of the nervous system using molecular, cellular, developmental, medical, and computational approaches.

Photo depicts scientist digging fossils out of the dirt. — Figure \(\PageIndex{11}\): Researchers work on excavating dinosaur fossils at a site in Castellón, Spain. (credit: Mario Modesto)

Paleontology, another branch of biology, uses fossils to study life’s history (Figure \(\PageIndex{11}\)). Zoology and botany are the study of animals and plants, respectively. Biologists can also specialize as biotechnologists, ecologists, or physiologists, to name just a few areas. This is just a small sample of the many fields that biologists can pursue.

Biology is the culmination of the achievements of the natural sciences from their inception to today. Excitingly, it is the cradle of emerging sciences, such as the biology of brain activity, genetic engineering of custom organisms, and the biology of evolution that uses the laboratory tools of molecular biology to retrace the earliest stages of life on earth. A scan of news headlines—whether reporting on immunizations, a newly discovered species, sports doping, or a genetically-modified food—demonstrates the way biology is active in and important to our everyday world.

Summary

Biology is the science of life. All living organisms share several key properties such as order, sensitivity or response to stimuli, reproduction, growth and development, regulation, homeostasis, and energy processing. Living things are highly organized parts of a hierarchy that includes atoms, molecules, organelles, cells, tissues, organs, and organ systems. Organisms, in turn, are grouped as populations, communities, ecosystems, and the biosphere. The great diversity of life today evolved from less-diverse ancestral organisms over billions of years. A diagram called a phylogenetic tree can be used to show evolutionary relationships among organisms.

Biology is very broad and includes many branches and subdisciplines. Examples include molecular biology, microbiology, neurobiology, zoology, and botany, among others.

Art Connections

Figure \(\PageIndex{7}\): Which of the following statements is false?

Tissues exist within organs which exist within organ systems.
Communities exist within populations which exist within ecosystems.
Organelles exist within cells which exist within tissues.
Communities exist within ecosystems which exist in the biosphere.

Answer: Communities exist within populations which exist within ecosystems.

Glossary

atom: smallest and most fundamental unit of matter

biochemistry: study of the chemistry of biological organisms

biosphere: collection of all the ecosystems on Earth

botany: study of plants

cell: smallest fundamental unit of structure and function in living things

community: set of populations inhabiting a particular area

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

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

evolution: process of gradual change during which new species arise from older species and some species become extinct

homeostasis: ability of an organism to maintain constant internal conditions

macromolecule: large molecule, typically formed by the joining of smaller molecules

microbiology: study of the structure and function of microorganisms

molecule: chemical structure consisting of at least two atoms held together by one or more chemical bonds

molecular biology: study of biological processes and their regulation at the molecular level, including interactions among molecules such as DNA, RNA, and proteins

neurobiology: study of the biology of the nervous system

organ: collection of related tissues grouped together performing a common function

organ system: level of organization that consists of functionally related interacting organs

organelle: small structures that exist within cells and carry out cellular functions

organism: individual living entity

paleontology: study of life’s history by means of fossils

phylogenetic tree: diagram showing the evolutionary relationships among various biological species based on similarities and differences in genetic or physical traits or both; in essence, a hypothesis concerning evolutionary connections

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

prokaryote: single-celled organism that lacks organelles and does not have nuclei surrounded by a nuclear membrane

tissue: group of similar cells carrying out related functions

zoology: study of animals