What are the 2 main categories of ecosystems

Terrestrial

Terrestrial ecosystems are land systems such as forests, deserts, grasslands, tundras and coastal regions. Depending on the biome's climate, more than one terrestrial ecosystem can be present. For example, tundras have less plant life because of lower temperatures; deserts produce fewer plants because of higher temperatures. A forest or grassland may have an extreme variety of plant life because its biome has the right amount of sunlight and moisture for many ecosystems, and species, to grow.

Lentic

Lentic is a class of aquatic ecosystems that are found on land, such as ponds, rivers, lakes, swamps and streams. Mostly, lentic ecosystems are described as still bodies of fresh water, and they are smaller ecosystems. Some lentic ecosystems contain animals and microorganisms, but they mostly rely on photosynthesis of algae and underwater plants to produce energy to thrive. One of the requirements of a lentic body of water is that it is exposed to the sun to encourage photosynthesis.

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a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.