Biology  5/e   Raven/Johnson
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Alternation of generations: Some organisms have two distinctly different generations, one haploid and one diploid, that occur alternately. One generation reproduces sexually, and the other asexually.

Evolutionary history of plants: Plants were the first organisms to colonize land, which they did about 410 million years ago. The first plants were multicellular with the capability of making their own food and conserving water. Within the next 100 million years, the plants were very diverse and forming large forests. Such forests were primarily horsetails, ferns, and primitive seed plants. By about 250 million years ago, conifers predominated in the cooler, drier climate. The earliest flowering plants appeared about 127 million years ago.

Classification: Scientists have evolved a classification system that attempts to classify organisms according to phylogeny. Organisms are classified into groups listed here in descending order: Kingdom, phylum or division, class, order, family, genus, and species.

Green algae: Green algae, believed to be the ancestors of plants, range in complexity from unicellular to multicellular. Their cell walls and photosynthetic pigments are very similar to those of plants.

Mycorrhizae: Mycorrhizae are fungal symbionts that enter or attach to roots of plants and aid them in the up-take of phosphorous and other ions.

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