archaea

reproduction

Like bacteria, reproduction in archaea is asexual. Archaea can reproduce through binary fission, where a parent cell divides into two genetically identical daughter cells. Archaea can also reproduce asexually through budding and fragmentation, where pieces of the cell break off and form a new cell, also producing genetically identical organisms.

what are archaea

For many years, archaea were classified as bacteria. Like the bacteria, archaea lacked a nucleus and membrane- bound organelles and, therefore, were prokaryotic cells. However, when scientists compared the DNA of the two prokaryotes, they found that there were distinct differences. They concluded that there must be two distinct types of prokaryotes, which they named archaea and bacteria. Even though the two groups might seem similar, archaea have many features that distinguish them from bacteria: 1. The cell walls of archaea are distinct from those of bacteria. While bacteria have cell walls made up of the polymer peptidoglycan, most archaea do not have peptidoglycan in their cell walls. 2. The plasma membranes of the archaea are also made up of lipids that are distinct from those in bacteria. 3. The ribosomal proteins of the archaea are similar to those in eukaryotic cells, not those in bacteria. Although archaea and bacteria share some fundamental differences, they are still similar in many ways: 1. They both are single-celled, microscopic organisms that can come in a variety of shapes ( Figure 1.1). 2. Both archaea and bacteria have a single circular chromosome of DNA and lack membrane-bound organelles. 3. Like bacteria, archaea can have flagella to assist with movement. Archaea shapes can vary widely, but some are bacilli (rod-shaped).

textbook_image

obtaining food and energy

Most archaea are chemotrophs and derive their energy and nutrients from breaking down molecules in their envi- ronment. A few species of archaea are photosynthetic and capture the energy of sunlight. Unlike bacteria, which can be parasites and are known to cause a variety of diseases, there are no known archaea that act as parasites. Some archaea do live within other organisms. But these archea form mutualistic relationships with their host, where both the archaea and the host benefit. In other words, they assist the host in some way, for example by helping to digest food.

instructional diagrams

No diagram descriptions associated with this lesson

questions

archaea are bacteria.

a. true

-->  b. false

archaea are single-celled prokaryotes.

-->  a. true

b. false

which of the following statements is true?

a) some archaea are able to photosynthesize.

b) archaea can easily form mutualistic relationships.

c) no known archaea cause disease.

-->  d) all of the above are true.

why are archaea considered prokaryotes?

a) they have cell walls.

-->  b) they lack a nucleus.

c) they are single-celled organisms.

d) all of the above

what methods of reproduction are observed in archaea?

a) budding

b) fragmentation

c) binary fission

-->  d) archaea reproduce through all of the above methods.

how are archaea similar to bacteria?

a) they have similar cell walls.

-->  b) they are both prokaryotic organisms.

c) they both have dna.

d) all of the above

why are archaea considered to be distinct from bacteria?

a) archaea lack a nucleus and membrane-bound organelles.

b) bacteria do not have a cell wall.

c) bacteria do not have ribosomes.

-->  d) they have distinct differences in their dna.

diagram questions

No diagram questions associated with this lesson