Directions of evolution, history of the organic world

A. N. Severtsov and I. I. Schmalhausen identified the main directions of evolution.

• Aromorphosis: a general increase in the complexity of structure. It leads to the emergence of new large groups (four-chambered heart, warm-bloodedness, flower and fruit).
• Idioadaptation: adaptation to a particular environment, structure does not become more complex.
• General degeneration: structure becomes simpler. For example, the parasitic tapeworm.

History of the organic world

It is divided into eras:

1. Archean: prokaryotes
2. Proterozoic: eukaryotes and multicellular organisms appear
3. Paleozoic: fish, amphibians (plants and animals come onto land)
4. Mesozoic: reptiles (age of gymnosperms)
5. Cenozoic: mammals, humans (dominance of flowering plants)

Key facts

• Signs of biological progress: an increase in the number of species, expansion of the range (area of distribution), growth in the number of individuals.
• The age of the Earth is ≈ 4,6 billion years. The first traces of life date to ≈ 3,5 billion years ago (prokaryotes). Photosynthesis began with cyanobacteria.
• Paleozoic: psilophytes, fish, amphibians, and in the Carboniferous, forests of ferns.
• Mesozoic: the age of reptiles. Dinosaurs, birds and mammals appeared.
• Example of aromorphosis: warm-bloodedness, breathing with lungs, independence of fertilization from water (seed).
• Example of idioadaptation: protective coloration, adaptation of plant fruits to dispersal by wind or animals.
• Humans appeared in the Cenozoic era (Homo sapiens), in the Quaternary period.