Climate Zones Objectives: 1. Describe Earth's major climate zones. 2. Explain how climate zones are characterized. Notes: According to the three cell convection model of each hemisphere the Earth neatly separates itself into three distinct climate zones; the polar, temperate, and the tropical zones.limate Zones Objectives: 1. Describe Earth's major climate zones. 2. Explain how climate zones are characterized. Notes: According to the three cell convection model of each hemisphere the Earth neatly separates itself into three distinct climate zones; the polar, temperate, and the tropical zones.
The nucleus is a large roundish organelle. It is bounded by a double membrane which has numerous pores. Inside the nucleus are chromosomes and a dark region called a nucleolus which makes ribosomes. (Ribosomes are necessary for protein synthesis.)
In eukaryotes, ribosomes float in the cytosol of a cell or bind to the endoplasmic reticulum (ER), ribbon-like structures found within the cell. Ribosomes are composed of two rRNA subunits and other catalytic proteins. They are quite small, only a few hundred nanometers across.