Answer:
Rivers often start from the mountain streams and contain high amounts of oxygen. Rivers and streams grow larger as these waters merge. Rivers pick up sediments from the land as they flow. Lakes support many varieties of organisms, including plants in shallow, open water and wetlands. In shallow water near shore, plankton is covered in water all or some of the time and are found along the edge of lakes and the floodplains of rivers. A deer is nibbling moss on rocks beside a river. Rivers are a major source of water for a variety of animals and plants.
Keywords
- Mountain streams
- Oxygen
- Merge
- Sediments
- Plants
- Wetlands
- Plankton
Explanation:
Freshwater ecosystems are of great importance for the diversity of plants and animals; they are also of the utmost importance for people as they are used in various ways. There are differences between freshwater ecosystems and marine ecosystems; the latter cantains a large number of salts, while the freshwater ecosystem does not provide.
Freshwater ecosystems are made up of rivers, lakes, streams, among others.
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Answer:
Oncogenes result from a mutation in proto-oncogenes.
Explanation:
- Protooncogenes control the growth and division of cells.
- The proteins encoded by proto-oncogenes include growth factors, growth factor receptors, transcription factors and signal transducers.
- They contribute to the transformation process by driving cell proliferation or reducing sensitivity to cell death.
- Several types of genetic and epigenetic changes convert these proto-oncogenes to oncogenes.
- Oncogenes arise due to the changes that increases the expression of proto-oncogenes .
- Oncogenes are one of the causes of cancers.
A proto-oncogenes can turn into oncogene by following ways:
- A point mutation such as deletion, insertion and substitution in the proto-oncogene can lead to formation of oncogenes.
- Chromosomal translocation may result in activation of proto-oncogene as seen in Burkitt's lymphoma.
- Insertion of a mobile genetic material such as retrovirus changes the gene expression, but leaves their coding sequence intact.
- Activation of proto-oncogene can also occur from reduplication and amplification of DNA sequence.
<span>Geologists generally know the age of a rock by determining the age of the group of rocks, or formation, that it is found in. The age of formations is marked on a geologic calendar known as the geologic time scale. Development of the geologic time scale and dating of formations and rocks relies upon two fundamentally different ways of telling time: relative and absolute.</span>
Answer:
During mitosis, the spindle fibers are called the mitotic spindle. ... Long protein fibers called microtubules extend from the centrioles in all possible directions, forming what is called a spindle. Some of the microtubules attach the poles to the chromosomes by connecting to protein complexes called kinetochores.
Spindle fibers move chromosomes during cell division by attaching to chromosome arms and centromeres. A centromere is the specific region of a chromosome where duplicates are linked. Identical, joined copies of a single chromosome are known as sister chromatids
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