Transcript Life: The Science of Biology, 8e

What is Biology?
Biology: the scientific study of living things
• Life can be defined as an organized genetic unit
capable of metabolism, homeostasis, reproduction, and
evolution.
• Life is incredibly diverse and complex, and not all
organisms display all these characteristics of life all the
time.
Living things: all the organisms descended
from a single-celled ancestor.
• All are composed of cells.
• A cell is the basic fundamental unit of life.
What is Biology?
Characteristics of living organisms:
• Consist of one or more cells
• Contain genetic information that allows them
to reproduce themselves
• Grow, develop and have a limited life span
• Are genetically related and have evolved
• Have the ability to adapt
What is Biology?
Characteristics of living organisms:
• Can obtain and use materials and energy.
(nutrients converted into ATP)
• Exchange gases such as oxygen and carbon
dioxide
• Respond to their environment
• Can regulate their internal environment –
maintain homeostasis
What is Biology?
Evolution: a central theme
Living systems evolve through differential
survival and reproduction.
The Many Faces of Life (Part 1)
The Many Faces of Life (Part 2)
What is Biology?
Unicellular organisms: a single cell
carries out all the functions of life
Multicellular organisms: made of many
cells that are specialized for different
functions
All Life Consists of Cells
The study of cells was made possible by the invention of the microscope.
• Discovery of cells was made possible by the invention of the microscope in
the 1590s by Dutch spectacle makers Zaccharias and Hans Janssen.
• The first biologists to improve and apply this technology to living organisms
were Antony van Leeuwenhoek and Robert Hooke in the late 1600s.
• Hooke coined the term cells to describe the repeated structures he saw in
cork tissue.
What is Biology?
Cell Theory:
• Cells are the basic structural and
physiological units of all living
organisms.
• Cells are both distinct entities and
building blocks of more complex
organisms.
(Schleiden and Schwann 1838)
What is Biology?
Cell Theory:
• All cells come from preexisting cells.
• All cells are similar in chemical composition.
• Most of the chemical reactions of life occur
within cells.
• Complete sets of genetic information are
replicated and passed on during cell division.
What is Biology?
Charles Darwin proposed that all living
organisms are descended from common
ancestors.
Evolution by natural selection
What is Biology?
Species: a group of organisms that look
alike and can breed successfully with
one another.
What is Biology?
Humans select for desired traits when
breeding animals.
Darwin postulated that natural selection
could occur through differential survival
and reproductive success.
What is Biology?
Traits that increase the probability that
the organism will survive and reproduce
will become more common in the
population.
Natural selection leads to adaptation.
Adaptations to the Environment
What is Biology?
DNA: the information that is passed from
parent to daughter cells
Genome: sum total of all the DNA in the
cell
All cells in a multicellular organism have
the same genome.
What is Biology?
DNA: repeating subunits—nucleotides
Gene: a specific segment of DNA
molecule—contains information for
making proteins
Mutations are alterations in the
nucleotide sequence.
The Genetic Code Is Life’s Blueprint
What is Biology?
Cells acquire nutrients from their
environment.
Nutrients supply energy and materials for
building biological structures
(synthesis).
Nutrient molecules contain energy in the
chemical bonds.
Energy from Nutrients Can Be Stored or Used Immediately
What is Biology?
Living organisms control their internal
environment.
Multicellular organisms have an internal
environment that is not cellular.
Cells are specialized, and organized into
tissues, tissues are organized into
organs.
Biology Is Studied at Many Levels of Organization
What is Biology?
Living organisms interact:
They may be territorial or they may
cooperate.
Figure 1.7 Conflict and Cooperation
What is Biology?
Individuals are part of populations.
Interacting populations of many different
species form a community.
Interacting communities in a given area
form ecosystems.
How is All Life on Earth Related?
Life arose by chemical evolution.
Molecules that could reproduce
themselves were critical.
Biological molecules were then enclosed
in membranes.
Life’s Calendar
How is All Life on Earth Related?
For 2 billion years, life consisted of single
cells—prokaryotes.
These cells were in the oceans, protected
from UV radiation.
How is All Life on Earth Related?
Metabolism: the sum of all chemical
reactions that occur in cells.
Photosynthesis evolved about 2.5 billion
years ago.
Photosynthetic Organisms Changed Earth’s Atmosphere
The first photosynthetic cells were similar to cyanobacteria.
How is All Life on Earth Related?
Consequences of photosynthesis:
• O2 accumulated in the atmosphere
• Aerobic metabolism began
• Ozone layer formed—allowed
organisms to live on land
How is All Life on Earth Related?
Eukaryotic cells evolved from prokaryotes.
Organelles—membrane bound
compartments with specialized functions:
• Nucleus
• Chloroplast