unit 2 themes and tools for studying biology

1.1 The Study of Life

KEY CONCEPTTechnology continually changes the way biologists work.


Imaging technologies provide new views of life.

• A microscope provides an enlarged image of an object.

stoma

– light microscopes (LM)


stoma

– scanning electron microscopes (SEM)





– transmission electron microscopes (TEM)

stoma

– scanning electron microscopes (SEM)





• Imaging technology is used in medicine.

– X-ray images


– magnetic resonance imaging (MRI)


– X-ray images


– functional MRI (fMRI)

– magnetic resonance imaging (MRI)


– X-ray images


Complex systems are modeled on computers.

• Computer models are used to study systems that cannot be studied directly.– heart attacks

– effect of medicines on the human body

– movement of water molecules into and out of a cell

– spread of a disease through a population

• Computer models are used when experiments are not safe, ethical, or practical.

Normal heartbeat

Heart attack


The tools of molecular genetics give rise to new biological studies.

• A gene is a segment of DNA that stores genetic information.


• Through our understanding of DNA, we can study genetics on a molecular level.

– molecular genetics– genomics


KEY CONCEPTUnderstanding biology can help you make informed decisions.


Your health and the health of the environment depend on your knowledge of biology.

• Knowledge of biology helps you understand your health.– food allergies– potential effects of obesity


– cancer

• Knowledge of biology helps you understand your health.

– effects of alcohol, tobacco, and other drugs

brain

lungs

heart

liver

kidneys

– food allergies– potential effects of obesity


• Knowledge of biology can help you understand environmental issues.– interactions in ecosystems

– biodiversity

– pollution


Biotechnology offers great promise but also raises many issues.

• Biotechnology is the use and application of living things and biological processes.


– DNA testing in medicine and forensics

• Biotechnology is the use and application of living things and biological processes.

– transgenic (genetically modified) crops– transgenic bacteria


• Questions are raised about the use of biotechnology.

– spread of undesirable genes– decrease in biodiversity– ethical considerations

– safety of genetically modified crops


Biology presents many unanswered questions.

• Over the past 50 years, biological knowledge has greatly increased.


• There are still many questions to answer in biology.

– How are memories stored in the brain?


• There are still many questions to answer in biology.

– How are memories stored in the brain?

surface proteins

lipid

envelope

nucleic acid capsid

– Does life exist on planets other than Earth?

– How do viruses mutate?


KEY CONCEPTAll living things are based on atoms and their interactions.


Living things consist of atoms of different elements.

• An atom is the smallest basic unit of matter.• An element is one type of atom.

H

O

Hydrogen atom (H)

Oxygen atom (O)


– The nucleus has protons and neutrons.– Electrons are in energy levels outside nucleus.

Oxygen atom (O)

Nucleus:8 protons (+)8 neutrons

outermost energy level: 6 electrons (-)

inner energy level: 2 electrons (-)

• An atom has a nucleus and electrons.


– water (H2O)

OHH

_

++

• A compound is made of atoms of different elements bonded together.


– carbon dioxide (CO2)


– water (H2O)


– many other carbon-based compounds in living things


– water (H2O)

– carbon dioxide (CO2)


Ions form when atoms gain or lose electrons.

• An ion is an atom that has gained or lost one or more electrons.– positive ions– negative ions

• Ionic bonds form between oppositely charged ions.

Sodium atom (Na) Chlorine atom (CI) Sodium ion (Na+) Chloride ion (CI-)

Na loses anelectron to CI ionic bond

gained electron


Atoms share pairs of electrons in covalent bonds.

• A covalent bond forms when atoms share a pair of electrons.

covalent bonds

Oxygen atom (O) Carbon atom (C) Oxygen atom (O)

Carbon dioxide (CO2 )

– multiple covalent bonds– diatomic molecules


KEY CONCEPTWater’s unique properties allow life to exist on Earth.


OHH

_

++

Life depends on hydrogen bonds in water.

• Water is a polar molecule.– Polar molecules have slightly charged regions.

– Nonpolar molecules do not have charged regions.– Hydrogen bonds form between slightly positive

hydrogen atoms and slightly negative atoms.


• Hydrogen bonds are responsible for three important properties of water.– high specific heat– cohesion– adhesion


Many compounds dissolve in water.

• A solution is formed when one substance dissolves in another.– A solution is a homogeneous mixture.– Solvents dissolve other substances.– Solutes dissolve in a solvent.

solution


• “Like dissolves like.”

– Polar solvents dissolve polar solutes.– Nonpolar solvents dissolve nonpolar solutes.– Polar substances and nonpolar substances generally

remain separate.


Some compounds form acids or bases.

• An acid releases a hydrogen ion when it dissolves in water.– high H+ concentration– pH less than 7

more acidic

stomach acid pH between 1 and 3


• A base removes hydrogen ions from a solution.

– low H+ concentration– pH greater than 7

bile pH between 8 and 9

more basic


• A neutral solution has a pH of 7.

pure water pH 7

unit 2 themes and tools for studying biology

Documents

new views of life

stomaimaging technologies

way biologists work

key concepttechnology

enlarged image

light microscopes lm