Biology 2201 Unit 2- Biodiversity. Classifying Living Things Ch. 4 – Patterns of Life Ms. K. Morris – 2010-2011. Section 4.1 - Characteristics of Life. Characteristics of Living Things (p.104). Living Things: Organized systems made up of one or more cells
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Classifying Living Things
Ch. 4 – Patterns of Life
Ms. K. Morris – 2010-2011
Soon biologists identified two more kingdoms: Fungi, which included mushrooms and moulds, and Bacteria, which lack a nucleus.
Taxonomy - the practice of classifying organisms. It is the branch of biology that deals with the classification and naming of living things.
Binomial Nomenclature - a classification system, a standard naming method used by scientists when referring to organisms.
The scientific name can be abbreviated by using the first letter of the genus name followed by the species name. This is usually done when the genus name is being repeated in a written document.
Scientific names: Advantages of binomial nomenclature
New biochemical evidence now tells us that it is more closely related to spiders than to crabs.
The new six kingdom classification system still has its limits and there are anomalies that don t fit nicely into it.
The seven major levels of the classification system are, from largest group to most specific are:
A memory device for memorizing the order of the levels is remembering the sentence:
Each group is smaller than the last. Organisms placed into the lower groups together are very closely related while organisms placed into groups at the higher levels share some common characteristics but are not necessarily similar.
When classifying organisms, taxonomists use a combination of information, including: (p. 113-116)
Classification systems improved as a result of the development of modern techniques.
There is one group of organisms that are not considered to be living things and that is the viruses.
- Refer to page 122 in textbook for examples.
Have only two things in common with living things:
1. Capsid - outer protein capsule which protects the genetic material. It helps to anchor the virus to the host cell during reproduction. Capsids vary in shape with the type of virus: (see fig 4.20, p. 122)
2. Genetic material (nucleic acid DNA or RNA - the genes of the virus)
1. attach to a host cell
2. get inside of the host cell
3. use the energy and organelles of the host cell to reproduce new viruses. The viral genetic material attaches to the cells genetic material, then commands the cells organelles to start manufacturing viruses.
Two methods to enter:
1. Attach and inject its nucleic acid (genetic material) into the host cell.
2. Attach and let the host cell form a vesicle around it. The cell takes it in by phagocytosis.
Viruses often only infect certain species they are adapted to. Viruses may infect
(a) only a particular species
(b) only plants and animals
(c) only plants and fungi
(d) only certain cell types in an organism
(e.g. the polio virus only infects nerve cells and intestinal cells)
A. Virus attaches to host cell.
B. Injects it nucleic acid into the host.
C. Viral genes take over the cells nucleus, forcing the cell to replicate virus genetic material. The host cells energy and organelles complete the task.
D. Assembly of new viruses. The cells organelles form protein capsids around viral nucleic acid.
E. Lysis and release. The cell eventually bursts, releasing new viruses. (Lysis = burst)