| The Eukaryotes |
The Eukaryotes: Fungi, Algae, Protozoa and Helminths
- The DNA in eukaryotes is complexed with
histones which are proteins. Eukaryote
chromosomes and complexed proteins form
chromatin and is located in the cells
nucleus.
- Some eukaryotic DNA can be found in
chloroplasts and mitochondria. These
organelles reproduce by binary fission.
- Eukaryote asexual reproduction includes:
binary fission, budding, fragmentation,
spore formation and schizogony.
- Sexual reproduction involves the
formation of gametes. Fusions of gametes
and formation of a zygote.
- Algae, fungi and some protozoa reproduce
both sexually and asexually
- In meiosis a diploid parent cell creates
four haploid daughter cells. The DNA has
usually undergone some crossing over so the
chromosomes are not only halved but are also
changed through rearrangement.
- Mitosis: Cells have two main stages in
the life cycle. Interphase: the
cells grow and duplicate their DNA, in the
second stage the cell�s nucleus divides. In
mitosis nuclear division starts after the
cell has duplicated its DNA. The result is
two exact copies of the DNA.
- One of each copy goes to the new cells
nucleus. Mitosis maintains the ploidy of a
cell. That is a haploid nucleus undergoing
mitosis creates two identical cells each
with a haploid nucleus. A diploid nucleus
undergoing mitosis creates two identical
cells each with a haploid nucleus.
- Asexual reproduction, in which a cell
undergoes multiple mitoses creating a
multinucleate cell is called a schizont.
This multinucleate cell then simultaneously
releases many uninucleate daughter cells
called merozoites. Plasmodium, which causes
malaria, reproduces this way inside red
blood cells and within the liver. The huge
release of merozoites results in the cyclic
fever and chills associated with malaria.
- Modern (early) 21st century
classification is based on DNA and protein
sequence information. This information
combined with existing taxonomic information
has resulted in new divisions and
classifications. The kingdom Protista was
reclassified into several new kingdoms:
Alveolata, Euglenozoa, Diplomonadida and
Parabasala. In the current classification
scheme Algae are distributed in the
kingdoms: Stramenophila and Rhodophyta and
Plantae. Water molds belong to the kingdom
of Stramonophila and slime molds are in the
kingdom Mycetozoa.
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