Themes of Life - 1
Honors 227
Themes of Living Systems
1.
Living world is a hierarchical in nature, with each level of organization
building upon the previous level
2.
One of the consequences of living systems being hierarchical in nature is the
“emergent property” of each step of the hierarchy
3.
Cells are an organism’s basic unit of structure and function
4.
Continuity of life is based on information that is (i) transferred from
generation to generation (and over eons of time) and (ii) preserved/stored at
the molecular level in the form of DNA
5.
Structure at all levels of organization is clearly correlated with the functional
features of that level
6.
Organisms are “open systems”, allowing for organisms to interact
continuously with the environment
7.
Because of the “openness” of biological systems, the constant interplay with
the environment requires a well balanced regulatory capacity operating at all
levels of organization and characterized by the recurrence of homeostasis at
all levels of organization
8.
Diversity is a hallmark of living systems and yet the “other side of the coin” is
the immense underlying similarity that is characteristic of all living systems
9.
Living systems have the capacity to reproduce at all levels of organization
(molecular to organismal)
10.
Evolution is a cornerstone of biology, providing the mechanistic theory to
understand not only the diversity of life but (at the same time) the underlying
similarity among all living organisms
Themes of Life - 2
Lecture Outline
Themes in the Study of Living Systems
1.
The 21st Century will see remarkable advances in the biological sciences that will
profoundly influence all of our lives in ways that we can not even imagine at this
juncture…. this century will see the kind of advances (basic and applied) that were
the hallmark of physics in the 20th century
2.
Living world is a hierarchical in nature, with each level of organization building
upon the previous level
Community
Population
Organism
Organ
Tissue
Cell
Organelles
Biological Molecules
(Macromolecules)
Atoms
3.
One of the consequences of living systems being hierarchical in nature is the
“emergent property” of each step of the hierarchy
With each step up in the hierarchy, novel properties emerge that were not present
@ lower levels and were not predictable
Why: interaction among units
e.g., while cell is composed of billions of macromolecules, the assemblage of
these macromolecules in precise and pre-arranged ways results in the highly
ordered and complex machinery of a cell (sum greater than the parts)
4.
Cells are an organism’s basic unit of structure and function
Similar to the central role of ecosystems in ecology
Cell is (i) lowest level of structure capable of performing all life’s activities and
(ii) most common basic structure of all living organisms
Robert Hooke (1665)…description of cells in cork (assumption that cells were
unique to cork)
Themes of Life - 3
Anton von Leewenhook discovered cells in multiple organisms
Cell Theory:
5.
(i) ubiquitous nature of cells in all organisms
(ii) all cells come from previous cells
Continuity of life is based on information that is (i) transferred from generation to
generation (and over eons of time) and (ii) preserved/stored at the molecular level in
the form of DNA
Order in any system must originate from information and instructions that serve
as a template for arranging parts and processes in an organized way; in biological
systems, this information/instructions are encoded in DNA, which also serves as
the vehicle for inheritance across generations and over eons of time
Arrangement of DNA as building blocks of nucleotides in a manner similar to
letters in the alphabet
Example of RAT versus TAR versus ART
6.
Structure at all levels of organization is clearly correlated with the functional
features of that level
Observing structure provides a window on function since the shape size and
attributes must be “in tune” with function
Conversely, knowing function, one can infer some feature of structure
e.g., human eye, hand, leaf
7.
Organisms are “open systems”, allowing for organisms to interact continuously
with the environment
Unique feature of all organisms is that they continuously operate in the context of
the environment…always processing stimuli from the environment…this is a
characteristic of “open” systems
Discuss difference between open and closed systems (box analogy)
e.g.,
8.
leaf orientation to sun
eyes, ears
Because of the “openness” of biological systems, the constant interplay with the
environment requires a well balanced regulatory capacity operating at all levels of
organization
Themes of Life - 4
All organisms need a well orchestrated and controlled system to function
effectively…in living systems, this control is provided by regulatory processes
that operate at all levels of organization.
e.g., in cells, enzymes provide regulation of chemical reactions
at human level, discuss thermostatic control of body temperature
9.
Diversity is a hallmark of living systems and yet the “other side of the coin” is the
immense underlying similarity that is characteristic of all living systems
Diversity is a hallmark of life
1.5 M known species
100 M thought to exist
Underlying this immense diversity is a very striking unity at the molecular level
so that you are more nearly kin to squirrels, birds and rabbits (and even microbes
and plants) than you think
10. Reproduction can occur through a variety of means (simple is budding) and yet
most animal species use sexual reproduction characterized by (i) dimorphic sexes
and (ii) re-shuffling of genetic material in the creation of offspring (recombination).
The latter is a phenomenally important underpinning of the evolution of life on
earth (more later)
11. Evolution is a cornerstone of biology, providing the mechanistic theory to
understand not only the diversity of life but (at the same time) the underlying
similarity among all living organisms
Theories in biology are difficult to have stood the test of time and even more
difficult to be able to address very divergent aspects of biological systems.
Evolution theory is one of those long-standing theories that has the fascinating
and unusual feature of being able to explain not only the diversity of life but also
(and at the same time) the fact that there is striking similarity among all living
forms
Charles Darwin (1859) and the Origin of Species