what characteristics must an object possess to be considered alive
Listing the defining characteristics of biological life
Biological science is the science that studies life, just what exactly is life? This may audio similar a silly question with an obvious response, but information technology is non e'er like shooting fish in a barrel to define life. For example, a co-operative of biological science called virology studies viruses, which showroom some of the characteristics of living entities simply lack others. It turns out that although viruses can attack living organisms, cause diseases, and even reproduce, they practice not meet the criteria that biologists use to define life. Consequently, virologists are non biologists, strictly speaking. Similarly, some biologists written report the early on molecular evolution that gave rising to life; since the events that preceded life are not biological events, these scientists are likewise excluded from biology in the strict sense of the term.
From its earliest beginnings, biology has wrestled with these questions: What are the shared backdrop that make something "live"? And once nosotros know something is alive, how practise we find meaningful levels of organization in its construction?
Learning Objectives
- List the backdrop of life
- Order the levels of organization of living things
Properties of Life
All living organisms share several key characteristics or functions: order, sensitivity or response to the environs, reproduction, growth and development, regulation, homeostasis, and energy processing. When viewed together, these characteristics serve to define life.
Order
Figure ane. A toad represents a highly organized structure consisting of cells, tissues, organs, and organ systems.
Organisms are highly organized, coordinated structures that consist of i or more cells. Even very simple, unmarried-celled organisms are remarkably complex: inside each cell, atoms brand upwardly molecules; these in plough make upwards prison cell organelles and other cellular inclusions.
In multicellular organisms (Figure 1), similar cells form tissues. Tissues, in turn, collaborate to create organs (body structures with a distinct function). Organs work together to form organ systems.
Sensitivity or Response to Stimuli
Organisms respond to diverse stimuli. For example, plants can bend toward a source of low-cal, climb on fences and walls, or respond to touch (Figure ii).
Figure 2.The leaves of this sensitive establish (Mimosa pudica) will instantly droop and fold when touched. After a few minutes, the plant returns to normal. (credit: Alex Lomas)
Fifty-fifty tiny bacteria can move toward or abroad from chemicals (a process calledchemotaxis) or light (phototaxis). Movement toward a stimulus is considered a positive response, while motility away from a stimulus is considered a negative response.
Sentry this video to see how plants respond to a stimulus—from opening to low-cal, to wrapping a tendril around a co-operative, to capturing casualty.
Reproduction
Single-celled organisms reproduce past first duplicating their Dna, so dividing it equally every bit the cell prepares to divide to form two new cells. Multicellular organisms often produce specialized reproductive germline cells that volition course new individuals. When reproduction occurs, genes containing DNA are passed along to an organism's offspring. These genes ensure that the offspring volition belong to the same species and will have similar characteristics, such equally size and shape.
Growth and Development
Figure iii. Although no 2 look alike, these puppies accept inherited genes from both parents and share many of the aforementioned characteristics.
Organisms grow and develop following specific instructions coded for by their genes. These genes provide instructions that will direct cellular growth and evolution, ensuring that a species' immature (Figure iii) will abound up to showroom many of the same characteristics equally its parents.
Regulation
Even the smallest organisms are complex and require multiple regulatory mechanisms to coordinate internal functions, respond to stimuli, and cope with environmental stresses. 2 examples of internal functions regulated in an organism are food send and blood flow. Organs (groups of tissues working together) perform specific functions, such as carrying oxygen throughout the body, removing wastes, delivering nutrients to every cell, and cooling the trunk.
Homeostasis
Effigy 4. Polar bears (Ursus maritimus) and other mammals living in ice-covered regions maintain their body temperature past generating oestrus and reducing rut loss through thick fur and a dense layer of fatty nether their pare. (credit: "longhorndave"/Flickr)
In club to function properly, cells need to have appropriate conditions such as proper temperature, pH, and appropriate concentration of diverse chemicals. These atmospheric condition may, however, change from one moment to the side by side. Organisms are able to maintain internal atmospheric condition within a narrow range almost constantly, despite environmental changes, throughhomeostasis (literally, "steady land")—the ability of an organism to maintain constant internal conditions. For example, an organism needs to regulate trunk temperature through a process known as thermoregulation. Organisms that live in common cold climates, such as the polar bear (Figure 4), have torso structures that assist them withstand low temperatures and conserve body heat. Structures that aid in this type of insulation include fur, feathers, blubber, and fatty. In hot climates, organisms have methods (such every bit perspiration in humans or panting in dogs) that assist them to shed backlog torso estrus.
Free energy Processing
All organisms use a source of energy for their metabolic activities. Some organisms capture energy from the sun and catechumen information technology into chemical free energy in food (photosynthesis); others apply chemical free energy in molecules they take in every bit food (cellular respiration).
Effigy 5. The California condor (Gymnogyps californianus) uses chemic energy derived from food to power flight. California condors are an endangered species; this bird has a wing tag that helps biologists identify the individual.
Levels of Organization of Living Things
Living things are highly organized and structured, following a hierarchy that can be examined on a scale from small to large. The cantlet is the smallest and most primal unit of matter. It consists of a nucleus surrounded by electrons. Atoms grade molecules. A molecule is a chemical structure consisting of at least two atoms held together by one or more chemic bonds. Many molecules that are biologically of import are macromolecules, big molecules that are typically formed by polymerization (a polymer is a large molecule that is fabricated by combining smaller units called monomers, which are simpler than macromolecules). An example of a macromolecule is dna (Deoxyribonucleic acid) (Figure 6), which contains the instructions for the structure and functioning of all living organisms.
Figure 6. All molecules, including this Dna molecule, are equanimous of atoms. (credit: "brian0918″/Wikimedia Commons)
Some cells contain aggregates of macromolecules surrounded by membranes; these are chosenorganelles. Organelles are small structures that exist inside cells. Examples of organelles include mitochondria and chloroplasts, which conduct out indispensable functions: mitochondria produce energy to power the cell, while chloroplasts enable dark-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 non considered living: they are not made of cells. To make new viruses, they have to invade and hijack the reproductive machinery of a living prison cell; only then tin can they obtain the materials they need to reproduce.) Some organisms consist of a single cell and others are multicellular. Cells are classified equally prokaryotic or eukaryotic. Prokaryotes are single-celled or colonial organisms that do not have membrane-bound nuclei or organelles; in dissimilarity, the cells of eukaryotes exercise have membrane-bound organelles and a membrane-bound nucleus.
In larger organisms, cells combine to maketissues, which are groups of similar cells carrying out similar or related functions. Organs are collections of tissues grouped together performing a mutual function. Organs are present non only in animals but also in plants. An organ system is a higher level of arrangement that consists of functionally related organs. Mammals have many organ systems. For instance, the circulatory organisation transports blood through the trunk and to and from the lungs; information technology includes organs such as the heart and blood vessels. Organisms are individual living entities. For instance, 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 chosen apopulation. For case, a forest may include many pine copse. All of these pine trees represent the population of pine trees in this forest. Different populations may live in the aforementioned 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 course the forest's community. The woods itself is an ecosystem. An ecosystem consists of all the living things in a particular expanse together with the abiotic, non-living parts of that environment such as nitrogen in the soil or rain water. At the highest level of organisation (Effigy 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 temper to a certain extent.
Practice Question
From a single organelle to the entire biosphere, living organisms are parts of a highly structured bureaucracy.
Effigy 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 Found; 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 piece of work by U.s.a. 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 inside organ systems.
- Communities exist within populations, which exist within ecosystems.
- Organelles exist inside cells, which be inside tissues.
- Communities exist within ecosystems, which exist in the biosphere.
Show Answer
Statement b is simulated: populations be within communities.
Check Your Understanding
Answer the question(southward) below to see how well you lot empathise the topics covered in the previous section. This short quiz doesnon count toward your grade in the class, and yous can retake it an unlimited number of times.
Use this quiz to check your understanding and make up one's mind whether to (1) study the previous department further or (ii) move on to the next department.
Source: https://courses.lumenlearning.com/suny-wmopen-biology1/chapter/the-characteristics-of-life/
0 Response to "what characteristics must an object possess to be considered alive"
Post a Comment