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Biology 1406
Chapter 1 – Evolution, the Themes of Biology, and Scientific
Inquiry
Biology – the study of life.
There are certain facts and concepts about biology that are going to be
central to the understanding of living things –
1. Life is a hierarchy – an order of ranks with each level building on
the levels below. Campbell speaks to this on P. 2-3:
A. The natural hierarchy
Fig. 1.3, P. 2-3 –
1. Biosphere – the highest level of the natural hierarchy
2. Ecosystem
3. Community
4. Population
5. Organism
6. Systems
7. Organs
8. Tissues
9. Cells
10. Organelles
11. Molecules
12. Atoms – the lowest level of the natural hierarchy
B. The man-made (Linnaean) hierarchy – for classification of life on Earth
Fig. 1.12, P. 10 –
1. Kingdom – this is the top level. It is the most inclusive level
This is one taxon that you are already familiar with – even in common
usage, we refer to the “plant kingdom” or the “animal kingdom”. At this
level, organisms are really, really different. Animals and plants differ at this
greatest and most all encompassing level.
2. Phylum
3. Class
4. Order
5. Family
6. Genus
7. Species – this is the lowest level. It is the most exclusive level
2. (P. 4) Structure and function are intimately related in living things.
Molecules and organisms both are shaped in order to perform the things they
do the best. Fish gotta swim and birds gotta fly. Both are adapted to their
environments and lifestyles – birds have light bones inside bodies that are
powerhouses of energy. In many instances, we have been able to deduce
much of how living things work by the way they are shaped or constructed.
Indeed, these kinds of structural and functional considerations lead to what
your text calls emergent properties (P. 3) – new and useful powers and
abilities based on the arrangement and interactions of the parts of a
system.
3. Cells are the basic unit of structure and function – the lowest level
of structure that we can say is alive. All organisms are either composed of
cells or are unicellular – one celled life forms.
Fig. 1.4 on P. 4
There are two kinds of cells –
Prokaryotic cells– like bacteria – very simple structure – nucleus not
contained within a membranous boundary.
Eukaryotic cells – everything else.
Cells are much more complex – have a real nucleus within a nuclear
envelope. You and I are eukaryotic!!
Prokaryotic cells – primitive, rudimentary, primordial nucleus
Eukaryotic cells – true, modern nucleus
4. (P. 5) DNA is the genetic material. All cells at some stage contain
DNA. DNA structure leads to DNA function – inheritance. This is based on
the ability of cells to copy the DNA faithfully, and to pass it on to the
offspring.
5. (P. 7-9) Living things interact with and draw sustenance from
their environment. All living things depend on each other for food which
supplies energy and material nutrients. Living things use the energy in their
environment to create orderly processes for themselves and return disorder
to their environment in order to get rid of it. (heat, waste products, etc.)
6. (P. 9 – 15) There is unity in diversity. All of biology is about this
topic – the most important concept in biology, because it explains how living
things that are so different can show so much similarity between them. The
term diversity refers to the millions of different species that exist – cows and
pea plants, mosquitoes and oak trees. In all this diversity, there is unity as
well. At the level of molecules, all living organisms use DNA as genetic
material, most organisms use oxygen to breath, and as you will see later this
semester, the genetic code is the same. This is best explained in biology by
Charles Darwin’s principles of evolution by natural selection, outlined for
you on P. 13 of your text. This is the single most important concept in all of
biology, and it has held up firmly to the most rigorous scrutiny of science for
the past 160 years. Evolutionary understanding brings sense to this hodge –
podge of diversity, and explains the underlying unity as well.