© 2014 pearson education, inc. 1.1 what is life? biology comes from the greek words “bio”...

© 2014 Pearson Education, Inc.

1.1 What Is Life?

Biology comes from the Greek words “bio” meaning “life” and “logy” meaning “the study of.” Organisms share common characteristics that, taken together, define life. Organisms:

Acquire and use materials and energy

Actively maintain organized complexity

Perceive and respond to stimuli

Grow

Reproduce

Have the capacity to evolve, collectively


1.1 What Is Life?

The cell is the basic unit of life

– It is separated from its surroundings by a membrane

– It encloses a variety of structures and chemicals in a fluid environment


Figure 1-1 The cell is the smallest unit of life

organelles

nucleus

cell wall

plasmamembrane


1.1 What Is Life?

Organisms acquire and use materials and energy

– Materials and energy are required for organisms to maintain organization, to grow, and to reproduce

– Important materials (minerals, water, & other simple chemical building blocks) are acquired from the air, water, soil, and bodies of other living things

– Organisms use energy continuously to sustain themselves


Figure 1-2 Properties of life

Eggs: livingthingsreproduce

Gut: livingthings acquirenutrients

Antennae andeyes: livingthings respondto stimuli


1.1 What Is Life?

Organisms acquire and use materials and energy (continued)

– Organisms obtain energy in two ways, coming directly or indirectly from the sun

– Photosynthesis is the process by which plants and some single-celled organisms capture sunlight

– Other organisms consume energy-rich molecules in the bodies of other organisms


Figure 1-3 The flow of energy and the recycling of nutrients


1.1 What Is Life?

Organisms actively maintain organized complexity

– Living things use energy on a continuous basis to self-sustain

– Cells pump chemicals in and out for appropriate chemical reactions to occur

– Organisms maintain relatively constant internal conditions or homeostasis


Figure 1-4 Organisms maintain relatively constant internal conditions


1.1 What Is Life?

Organisms perceive and respond to stimuli

– Organisms sense and respond to internal and external environmental stimuli

– Sensory organs in animals can detect and respond to external stimuli such as light, sound, chemicals, etc.

– Internal stimuli in animals are perceived by stretch, temperature, pain, and chemical receptors

– Plants and bacteria respond to stimuli as well (e.g., plants grow toward the light, and bacteria move toward available nutrients in a medium)


1.1 What Is Life?

Organisms grow

– Every organism becomes larger over time

– Plants, birds, and mammals grow by producing more cells to increase their mass

– Bacteria grow by enlarging their cells; they divide in half to reproduce after genetic material is copied

– Growth involves the conversion of acquired materials to molecules of the organism’s body


1.1 What Is Life?

Organisms reproduce

– Organisms reproduce by dividing in half, producing seeds, bearing live young, and laying eggs

– Organisms give rise to offspring of the same type

– The parent’s genetic material (DNA) is passed on to the offspring, creating continuity of life


Figure 1-6 Organisms reproduce

Dividing Streptococcusbacterium

Panda with its babyDandelion producingseeds


Figure 1-7 DNA


1.1 What Is Life?

Organisms, collectively, have the capacity to evolve

– Evolution is the process by which modern organisms descended, with modifications, from preexisting forms of life

– Changes in DNA within populations occur over the course of generations, which results in evolution

– Populations are groups of the same type of organism living in the same area


1.2 What Is Evolution?

Evolution explains the diversity of life on Earth

Evolution provides an explanation for the similarities found among different types of organisms

– Chimpanzees and people have various physical features in common

– DNA of humans differs from that of chimpanzees by less than 5%


Figure 1-8 Chimps and people are closely related



Three natural processes underlie evolution

– Genetic variation among members of a population due to differences in their DNA

– Inheritance of those variations by offspring of parents carrying the variation

– Natural selection of individuals whose survival and enhanced reproduction are due to the favorable variations they carry



Mutations are the original source of differences in DNA

– Variations are due to the differences in genes, which are components of DNA and the basic units of heredity

– Mutations occur when changes in genes are mistakenly copied

– Mutations can also result from DNA damaged by

– UV rays from sunlight and toxic chemicals from cigarette smoke



Some mutations are inherited

– Occur in sperm or egg cells

– Effects of mutation

– No effect (harmless)

– A decrease in the organism’s ability to function

– Death of the organism

– An increase in an organism’s ability to survive and reproduce (rare)



Some inherited mutations help individuals survive and reproduce

– Natural selection is the process by which organisms with certain inherited traits survive and reproduce better than others in a particular environment

– Organisms that best meet environmental challenges leave the most offspring

– Natural selection preserves genes that help organisms flourish



Some inherited mutations help individuals survive and reproduce (continued)

– Adaptations are structures, physiological processes, or behaviors that aid in survival and reproduction

– Adaptations that are good for one environment may be poor in another

– Species that cannot adapt to environmental change become extinct, as for example, the dinosaurs

– Extinction is the complete elimination of a particular species


Figure 1-9 A fossil Tyrannosaurus rex




– The many different habitats (environments) in an area coupled with evolutionary adaptive processes produce species variety, or biodiversity

– Humans are responsible for accelerating the rate of environmental change (and therefore, the rate of extinction of species)




– “Nothing in biology makes sense except in the light of evolution” Dobzhansky

– Darwin and Wallace formulated the basis of our modern understanding of evolution when they devised the theory of evolution in the mid-1800s

– Abundant evidence has been found to support evolutionary theory since the 1800s


Levels of biological organization

Fig. 1-10


1.3 How Do Scientists Study Life?

Life can be studied at different levels

– All matter is formed of elements

– An atom is the smallest particle of an element retaining the properties of an element

– Atoms combine to form molecules

– Molecules provide the building blocks for cells, the smallest unit of life



Life can be studied at different levels (continued)

– Some forms of life consist of single cells

– In multicellular forms, cells combine to form tissues

– Tissues combine to form organs, which can be united as organ systems

– Multicellular organisms are composed of multiple organ systems



Life can be studied at different levels (continued)

– Organisms of the same type that are capable of interacting and interbreeding are called a species

– A group of organisms of the same species living in a given area is a population

– Interacting populations make up a community

– A community and its nonliving environment is an ecosystem

– The entire surface of Earth, including living and nonliving components, is the biosphere



Biologists classify organisms based on their evolutionary relationships

– Scientists generally categorize organisms into three major groups, or domains

– Bacteria

– Archaea

– Eukarya

– The fundamental differences among cell types in organisms are reflected in classifications


Figure 1-11 The domains and kingdoms of life

FIRST CELLS

DO

MA

IN B

AC

TE

RIA

Protists

DO

MA

IN E

UK

AR

YA

DO

MA

IN A

RC

HA

EA

Plants

Fungi

Animals



Biologists classify organisms based on their evolutionary relationships (continued)

– Bacteria and Archaea are single, simple cells

– Eukaryotic organisms have one or more extremely complex cells

– The domain Eukarya contains four subdivisions or kingdoms

– Fungi

– Plantae

– Animalia

– Protists



Biologists classify organisms based on their evolutionary relationships (continued)

– Three characteristics underlie the classification of an organism into a domain and kingdom

– There are exceptions to any simple set of rules used to distinguish the domains and kingdoms, but three characteristics are particularly useful

– Cell type—simple or complex

– The number of cells in each organism—unicellular or multicellular

– Energy acquisition


Table 1-1



Cell type distinguishes the Bacteria and Archaea from the Eukarya

–All cells share common features

– Plasma membrane is a thin sheet of molecules surrounding the cell

– Organelles are specialized structures that carry out specific functions

– All cells contain DNA, the hereditary material



Cell type distinguishes the Bacteria and Archaea from the Eukarya (continued)

– The domains Bacteria and Archaea consist of prokaryotic cells

– The domain Eukarya is composed of eukaryotic cells




– Two cell types are seen among all living things: prokaryotic and eukaryotic cells

– Cell types are named after presence or absence of a nucleus

– The nucleus is a membrane-enclosed sac containing the cell’s genetic material




– Eukaryotic (“true nucleus” in Greek)

– They are larger than prokaryotic cells

– They contain a variety of organelles, including a nucleus

– This cell type is found only among members of the domain Eukarya

– They are extremely complex




– Prokaryotic (“before nucleus” in Greek)

– They are only 1–2 micrometers in diameter

– They lack organelles enclosed by membranes

– They lack a nucleus

– This cell type is found in the domains Bacteria and Archaea

– They are smaller and much simpler than the eukaryotic cell



Multicellularity occurs only among the Eukarya

– Unicellular (single-celled) organisms are found in

– Bacteria

– Archaea

– Multicellular (many-celled) organisms are found in Eukarya, within the kingdoms

– Fungi

– Plantae

– Animalia



The Eukarya acquire energy in different ways

– Autotrophs (“self-feeding”)

– Photosynthetic organisms that capture sunlight and store it in sugar and fats

– Includes plants, some bacteria, and some protists

– Heterotrophs (“other-feeding”)

– Organisms that acquire energy through ingesting molecules in the bodies of other organisms

– Includes many archaeans, bacteria, protists, fungi, and animals

– The size of the food eaten varies from individual food molecules to ingestion and digestion of whole chunks



Biologists use the binomial system to name organisms

– Organisms are placed in a hierarchy of categories

– Genus and species are the two smallest categories

– Genus includes many different species with similar characteristics

– Species includes organisms that can interbreed and are nearly identical



Biologists use the binomial system to name organisms (continued)

– Binomial system based on Latin words two (bi) and names (nomial), and consisting of the genus and species

– Genus name is capitalized

– Both genus and species names are italicized

– People are Homo sapiens


1.4 What Is Science?

Science is the systematic inquiry – through observation and experiment – into the origins, structure, and behavior of living and nonliving environments



Science is based on the principle that all events have natural causes

– The belief that some events happen through supernatural forces (e.g., the actions of Greek gods)

– The belief that all events can be traced to natural causes that we can comprehend (natural causality)

– Corollary: Evidence gathered from nature has not been deliberately distorted to fool us



The scientific method is an important tool of scientific inquiry

– The scientific method consists of six interrelated elements

– Observation

– Question

– Hypothesis

– Prediction

– Experiment

– Conclusion



The scientific method is an important tool of scientific inquiry (continued)

– Scientific inquiry is a rigorous method for making observations

– The scientific method for inquiry follows six steps



The six steps of scientific inquiry

1. Observation of a specific phenomenon

2. The observation, in turn, leads to a question

3. The question leads to formulation of a hypothesis, based on previous observations, which is offered as an answer to the question



The six steps of scientific inquiry (continued)

4. The hypothesis leads to a prediction, which isthe expected outcome of testing if the hypothesis is correct

5. The prediction is tested by carefully designed additional observations or carefully controlled manipulations called experiments

6. The experiments produce results that either support or refute the hypothesis, allowing the development of a conclusion



Biologists test hypotheses using controlled experiments

– Two types of situations are established

– A baseline or control situation in which all possible variables are held at a constant

– An experimental situation in which one factor, variable, is manipulated to test the hypothesis to determine that this variable is the cause of an observation

– Science is useless unless communicated

– The scientific method is illustrated by experiments by Francesco Redi and Malte Andersson


Figure E1-1 The experiment of Francesco Redi illustrates the scientific method

Observation:

Question:

Hypothesis:

Prediction:

Experiment:

Conclusion:

Experimental variable:

Controlled variables:

Experimental situationControl situation

Results

Leave the jaruncovered

Leave exposedfor several days

Flies swarm aroundand maggots appear

Cover the jarwith gauze

Leave coveredfor several days

Flies are kept fromthe meat;

no maggots appear

gauze prevents theentry of flies

time, temperature,place

Obtain identical pieces of meat and two identical jars

Place meat in each jar

IF the hypothesis is correct, THEN keeping the flies away from the meatwill prevent the appearance of maggots.

The experiment supports the hypothesis that flies are the source ofmaggots and that spontaneous generation of maggots does not occur.

Flies swarm around meat left in the open; maggots appear on the meat.

Where do maggots on the meat come from?

Flies produce the maggots.


Figure E1-2 The experiment of Malte AnderssonObservation:

Question:

Hypothesis:

Prediction:

Experiment:

Conclusion:

Experimentalvariable:

Controlledvariables:

Experimental groupsControl groups

Results

Do notchange the tail

Release the males,wait a week,

count the nests

Average ofabout one nest

per male

Male widowbirds have extremely long tails.

Why do males, but not females, have such long tails?

Males have long tails because females prefer to mate with long-tailed males.

IF females prefer long-tailed males, THEN males with artificially lengthened tails will attract more mates.

Divide male birdsinto four groups

Manipulate thetails of the males

length of tail

location, season,time, weather

Cut the tail andre-glue in place


count the nests

Average ofabout one nest

per male

Cut the tail to half ofthe original length


count the nests

Average of lessthan half a nest

per male

Add feathers todouble the tail length


count the nests

Average ofAbout two nests

per male

The hypothesis that female widowbirds prefer to mate with long-tailed males (and are less likely to matewith short-tailed males) is supported.



Scientific theories have been thoroughly tested

– A scientific theory is a general and reliable explanation of important natural phenomena that has been developed through extensive and reproducible observations and experiments

– A scientific theory is best described as a natural law, a basic principle derived from the study of nature, which has never been disproven by scientific inquiry



Scientific theories have been thoroughly tested (continued)

– The cell theory (that all living organisms are composed of cells) and the theory of evolution are fundamental to the study of biology

– Natural causality is the principle that all events can be traced to natural causes

– Natural laws apply to every time and place

– Scientific inquiry is based on the assumption that people perceive natural events in similar ways




– New scientific evidence may prompt radical revision of existing theory

– For example, the discovery of prions




– Before 1980, all known infectious diseases contained DNA or RNA

– In 1982, Stanley Prusiner showed that the infectious sheep disease scrapie is caused by a protein (a “protein infectious particle,” or prion)

– Prions have since been shown to cause “mad cow disease” and diseases in humans

– The willingness of scientists to revise accepted belief in light of new data was critical to understanding and expanding the study of prions



Scientific theories involve both inductive and deductive reasoning

– Inductive reasoning is used in the development of scientific theories

– A generalization is created from many observations that support it and none that contradict it

– For example, the theory that Earth exerts gravitational forces on objects began from repeated observations of objects falling downward toward Earth and from no observations of objects falling upward away from Earth



Scientific theories involve both inductive and deductive reasoning (continued)

– Deductive reasoning is the process of generating hypotheses based on a well-supported generalization (such as a theory)

– For example, based on the cell theory, any newly discovered organism would be expected to be composed of cells



Scientific theories are formulated in ways that can potentially be disproved

– Basic principles of science are referred to as theories because theories can be disproved or falsified

– Falsifying theories is distinctly different between scientific theories and faith-based beliefs

– “Each creature on Earth was separately created” cannot be subjected to scientific inquiry because it is a belief rooted in faith



Science is a human endeavor

– Human personality traits are part of “real science”

– Scientists, like other people, may be driven by pride, ambition, or fear

– Scientists sometimes make mistakes

– Accidents, lucky guesses, intellectual powers, and controversies with others contribute strongly to scientific advances



Science is a human endeavor (continued)

– In the 1920s, bacteriologist Alexander Fleming grew bacteria in cultures

– One of the bacterial cultures became contaminated with a mold

– Fleming was about to destroy the culture when he noticed the mold (Penicillium) inhibited bacterial growth in the culture




– Fleming hypothesized that the mold produced an antibacterial substance

– Further tests using broth from pure Penicillium cultures lead to the discovery of the first antibiotic, penicillin


Figure 1-12 Penicillin kills bacteria

A Petri dishcontains solidgrowth medium

Bacteria grow indense red colonieson the growth medium

A substance diffusesfrom the mold andkills the bacterialcolonies, which losetheir color as they die

A colony of themold Penicillium




– Fleming continued beyond a lucky “accident” with further scientific investigation to a great discovery

– “Chance favors the prepared mind” Louis Pasteur



Knowledge of biology illuminates life

– Science is NOT a dehumanizing activity


Figure 1-13 Adaptations in lupine flowers

Pollen is forcedonto the bee’sabdomen

© 2014 pearson education, inc. 1.1 what is life? biology comes from the greek words “bio”...

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