Learning Objective Chapter 1: Introduction to Biology Describe the...

Copyright © 2014 by John Wiley & Sons, Inc.

Introduction to Biology

Chapter 1: Introduction to Biology

1.1: Themes and Concepts of Biology

1.2: The Process of Science

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Introduction to Biology (1.1)

Learning Objective• Describe the properties and levels of organization of

living things

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Class Exercise: What does it mean to be living?

• Are you alive?

• Is fire alive?

• Is an egg alive?

• Is a car alive?

• Is a seed alive?

• Is a refrigerator alive?

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Properties of Life• Order

• Sensitivity or response to stimuli

• Reproduction

• Adaptation

• Growth and development

• Regulation

• Homeostasis

• Energy Processing

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Properties of Life• Order

– Order is the opposite of random• Order occurs when there is a specific

arrangement of items • Or in other words, order occurs when

items have a specific relationship to other items.

– A toad represents a highly organized structure consisting of

• cells – which are composed of an organized arrangement of molecules

• Tissues – which are composed of an organized arrangement of cells

• Organs – which are composed of an organized arrangement of tissues

• organ systems – which are composed of an organized arrangement of organs

– A toad is made up of the same stuff (atoms and molecules) as it’s nonliving environment but the parts are arranged in a very precise way and thus is significantly more ordered than its nonliving surroundings

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Properties of Life• Sensitivity or response to stimuli

– Stimuli are particular states or conditions in the environment that cause an organism to react in a particular way

• While lots of nonliving things can be moved by physical forces and in a sense react to the environment

– a rock on a cliff can fall, – sand can be blown by wind, etc,

• Unlike nonliving things, living things can move toward or away from something (or transport stuff into or out of itself) that is not itself the primary source of energy

– Plants grow toward light however, light in general does not cause non living things to move toward the light source

» In other words light is not pulling plants toward it

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

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Properties of Life• Reproduction

– Reproduction is the process of making more of the same kind of thing

– All living organisms contain the information required to make more of that type of organism

• This information is known as the genetic material• All living things use DNA as the way to store genetic information

(DNA is the genetic material)• DNA stores the “instructions” to make all the parts of the

organism from building blocks obtained from the environment– Not all organisms reproduce but they have the information

and all the machinery required to reproduce

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Introduction to Biology (1.1)Properties of Life

• Adaptation– As an environment changes, natural

selection causes the characteristics of the individuals in a population to track those changes

• If flowers get deeper, those hummingbirds with naturally longer beaks will survive and reproduce making offspring sharing similarly long beaks

– shorter beak hummingbirds will be less likely to get the nectar food source from deep flowers and more likely to die before producing any offspring

• Similarly, if the climate gets colder, polar bears with better insulation (fur and fat) will be more likely to survive and reproduce than those with less insulation. The next generation would then inherit the better insulation

• In both cases above, as the environment changes, the next generation has characteristics that are better in that environment (longer beaks; more insulation). This is adaptation

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Properties of Life• Growth and

development– All organisms go

through stages that are simpler and/or smaller to those that are larger and/or more complex as they acquire material from their environment

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Properties of Life• Regulation

– All living things control processes that affect how it functions

• Processes are started or stopped, increased or decreased based on the requirements of the organism

• Certain regulated processes lead to homeostasis (sweat production, muscle shivering) but not all do

– Cell division is a highly regulated process but doesn’t maintain any stable internal condition.

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Introduction to Biology (1.1)Properties of Life

• Homeostasis: – process of maintaining an internal

environment that is relatively stable • even when the external

environment changes significantly • Examples: pH of fluids, water/salt

balance, body temperature, etc.– Homeostasis is a result of

regulating particular processes. • For example, in the homeostasis of

body temperature, sweat production is regulated to cool the body when hot

– it is turned on when the body temperature of humans increases slightly and

– turned off when body temperature is normal or low.

– However, when overheated the production of sweat lowers the body temperature which maintains a stable body temperature (homeostasis)

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Properties of Life• Energy processing

– All organisms obtain and use energy from the environment

• Energy is used to maintain order by repairing structures Energy is used to move toward or away from stimuli

• Energy is used to acquire material from the environment to grow and develop

• Energy is used to maintain homeostasis

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Introduction to Biology (1.1)Hierarchy of properties of life

All of the properties of life can be thought of as a consequence of just two main properties: maintaining order and reproducing• Order

– Requires energy to keep order (energy processing)• For example, when things fall apart, energy and resources (molecules, atoms) are needed to put

back together– Need to get energy and resources from environment (respond to stimuli)

– Function determined by structure, structures are specific arrangements of “stuff” (order)• To function properly, processes need to keep important stuff inside and bad stuff outside (a type

of homeostasis) • A process needs to be turned on and off depending on particular conditions (regulation, also

response to stimuli)– For example, we eat to gain energy and resources from the environment, however, we turn on eating

behavior some of the time and turn it off other times (eating is regulated). » This is not exactly homeostasis but related to it. Eating is regulated because it is turned off and on

under certain conditions. However, it is often turned on to maintain homeostasis of blood sugar levels, …though you can eat even when blood sugar is high

• Reproduction based on a inherited information– After reproduction, organisms need to build themselves up from something simpler (growth

and development)• For example before a bacteria divides it acquires more stuff from the environment (growth) and

after it divides, it is smaller and simpler than the bacteria it came from (even if only slightly simpler)

• All sexually reproducing multicellular organism (most animals, plants and fungi) start off as a single cell (a fertilized egg)

– For anything that reproduces, if not all of the offspring can survive and reproduce themselves, then this leads to natural selection which causes adaptation. (more on this later)

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The simplest structure that has all the properties of life is a cell

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Cells• Cells are small

– most cells can only be observed under a microscope

• Robert Hooke first described cells in 1665

• Coined the term “cell” after looking at cork under a microscope and seeing structures looking like monastery cells

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Cells• Cells are fundamentally important to

life – All living things are composed of one or more cells

• Matthias Schleiden in 1838 recognized that cells were fundamental to plant composition

• Theodor Schwann in 1839 reported that all animal tissues are also composed of cells

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Cells

• Unified cell theory states the importance of cells to life

1. All organisms are composed of one or more cells

2. Cells are the smallest/simplest living things, the basic

unit of life

3. Cells arise only by division of previously existing cells

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Introduction to Biology (1.1)What is a Cell?• A cell is basically a watery sac of

chemicals that has all the properties of life.

• The surface of the sac is a thin oily layer that keeps the watery stuff in and other stuff out

• It contains all the information needed to build new cells

• The basic components of all cells– Has a cell membrane (the thin oily layer

that forms the outside of the watery sac)– It carries genetic information in the form

of DNA– It contains ribosomes to use the genetic

information to assemble proteins – It contains cytosol/cytoplasm which is the

watery gel like material on the inside of the cell where all the chemistry of life occurs

– It contains proteins that do work and carry out the cell functions

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Proteins

RNA

Properties of Life• Something must have ALL the characteristics of life to be

considered living

• The simplest collection of matter that exhibits all of the properties of life is the cell

– A virus is not a cell but shares many of the properties of life but not all,

• Thus, viruses are not alive• They are simply genetic information in a protein box• They do not have the biological machinery to make anything• Viruses basically inject genetic information into cells and hijack

the cells machinery to make more virus parts and virus particles

– Bacteria are organisms composed of a single prokaryotic cell. • Each bacteria exhibits all of the properties of life • The simplest living thing known is a bacteria • The first life on earth were likely bacteria• All living things share a common ancestor that was a bacteria but

diversified and became more complex through evolution

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Viruses Are Not Alive• Viruses are often considered on the cusp of life because

– They are ordered (complex and specific arrangement of molecules)

– They have genetic material– The population of viruses can adapt and evolve!!!!– They can “reproduce” …but not without hijacking a hosts

biological machinery!• Viruses do not:

– Reproduce independently – Have the ability to use energy to maintain order– Maintain homeostasis (no internal regulation)– Grow and develop– Respond to environmental stimuli (mostly)

• Binding to a host cell can trigger events that result in type of reponse in a virus, but it is very limited Influenza virus

Proteins

RNA

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Viruses Are Not Alive• Viruses are not living machines, they are just

inactive information in a box– At the core of all viruses is just genetic material

(can be RNA or DNA) in a protein container• Some viruses can be much more complex in the

type of container the genetic material is in.– Once a virus’ genetic material gets inside a cell,

the cell’s machinery is hijacked becoming a virus factory

Influenza virus

Proteins

RNA

Ebola virus

Envelope protein

Envelope (membrane)

Capsid (protein)

Enzyme (protein)

RNA (genetic material)

Human immunodeficiency virus (HIV)

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All Living Things Are Composed of

Cells

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• All Living Things Are Composed of Cells– Each cell is a small container of chemicals and water

wrapped in a thin oily membrane that can perform all the necessary functions to maintain life.

• We can distinguish two major types of cells:– The prokaryotic cell is

• simpler and usually smaller and

• characteristic of bacteria.

– The eukaryotic cell is• subdivided by internal membranes into

different functional compartments called organelles and

• found in plants and animals.

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Nucleoidregion Nucleus

Organelles

Prokaryotic cell (bacterium)

Smaller

Simpler structure

DNA concentrated in

nucleoid region, which isnot enclosed by membrane

No membrane bound organelles

•••

•

••

•

•

Larger

More complex

structure

DNA enclosed by

membrane (Nucleus)

Contains many types of organelles

Eukaryotic cell (animal)

Co

lori

zed

TE

M

1

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Learning Objective Chapter 1: Introduction to Biology Describe the...

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