Themes of Life

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Themes in the Study of Life

Campbell Biology 9th ed. Chapter 1

What is Biology?
• Biology is the scientific study of life
• Biologists ask questions such as




How do multicelled organisms develop?
How does the human mind work?
How do living things interact in communities?

• Life defies a simple, one-sentence
definition
• Life is recognized by what living things do

Some Properties of Life
• Order
• Evolutionary
adaptation
• Response to
environment
• Reproduction
• Growth and
development
• Energy processing
• Regulation

Biologists Study Life at
Different Levels
• The study of life can be divided into
different levels of biological organization
Levels range from molecules to the entire
living planet
• New properties emerge at each level in the
biological hierarchy
• All levels of biological organization interact with
each other


The biosphere

Levels
of Organization
Ecosystems

Tissues

Organs and
organ systems

Communities
Organelles
Organisms

Populations

Cells

Atoms
Molecules

Organisms Interact with Each
Other and the Environment
• Organisms and their environments are
affected by the interactions between them


A tree takes up water and minerals from the
soil and carbon dioxide from the air; the tree
releases oxygen to the air and roots help
form soil

• Interactions between organisms and their
environment form the basis of ecosystems

Sunlight
Leaves absorb
light energy from
the sun.

CO2

Leaves take in
carbon dioxide
from the air
and release
oxygen.

O2

Cycling
of
chemical
nutrients
Leaves fall to
the ground and
are decomposed
by organisms
that return
minerals to the
soil.

Water and
minerals in
the soil are
taken up by
the tree
through
its roots.

Animals eat
leaves and fruit
from the tree.

Living Organisms Need
Energy for Life’s Activities
• Energy is required for “work”


Movement, growth, reproduction, etc.

• Living organisms transform energy from
one form to another


Light energy → chemical energy →
kinetic energy

• Energy flows through an ecosystem


Enters as sunlight and exits as heat

Energy Flow and Transformation
Sunlight

Heat
When energy is used
to do work, some
energy is converted to
thermal energy, which
is lost as heat.

Producers absorb light
energy and transform it into
chemical energy.

An animal’s muscle
cells convert
chemical energy
from food to kinetic
energy, the energy
of motion.

Chemical
energy

Chemical energy in
food is transferred
from plants to
consumers.

(a) Energy flow from sunlight to
producers to consumers

(b) Using energy to do work

A plant’s cells use
chemical energy to do
work such as growing
new leaves.

Structure and Function are
Correlated at all Biological
Levels
• Structure and function of living organisms are
closely related


A thin flat leaf maximizes the capture of light by
chloroplasts



The structure of a bird’s wing is adapted to flight

The Cell Is an Organism’s
Basic Unit of Structure and
Function
• Performs all activities required for life
• All cells share certain characteristics




enclosed by a membrane
use DNA as genetic information
come from other cells

• There are two main forms of cells



Eukaryotic
Prokaryotic

Two Major Cell Types
• Prokaryotic cells



Lack membrane enclosed
organelles
EUKARYOTIC CELL
small

• Eukaryotic cells




Membrane

PROKARYOTIC CELL
DNA
(no nucleus)
Membrane

Cytoplasm

Subdivided by internal
membranes that form
membrane-enclosed
organelles
larger
Organelles
Nucleus (contains DNA)

1 µm

Heritable Information is
Encoded in DNA
• Chromosomes are composed of DNA
(deoxyribonucleic acid) and proteins
• Genes, are composed of DNA and are
transmitted from parents to offspring


genes are the units of inheritance

• Cell division is the...
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