Comparative anatomical evidence
Comparative anatomical evidence for evolution includes:
- a similar plan of the structure of organisms of different systematic groups;
- live transitional forms;
- homologous organs;
- similar bodies;
- rudiments;
- atavisms.
Living transitional forms are modern organisms that have signs of different systematic groups in their structure.
For example, in a lancelet, a single-layer skin epithelium, segmentation of muscles, organs of excretion and reproduction show its similarity with invertebrates, and the presence of a notochord, neural tube and branchial clefts – similarity with vertebrates.
Cycads growing in tropical forests have signs of ferns and gymnosperms in their structure. Large compound leaves and floating flagellate spermatozoa are common with ferns, but seed formation brings cycads closer to gymnosperms.
Homologous organs are organs that have a similar origin and structure, but perform different functions.
These organs develop from the same primordia, occupy the same place on the body, but outwardly differ. Allows you to establish family ties between organisms.
Examples:
- forelimbs of mammals (wing of a bat, pectoral fin of a whale, burrowing limb of a mole, human hand);
- leaf modifications in plants (cactus thorns, trapping leaves of a sundew, pea antennae, kidney scales, succulent bulbs scales).
Analogous organs are organs that have different origins and structures, but perform the same functions and have external similarities.
Similar organs are formed from different primordia in unrelated groups of organisms. They can occupy different positions on the body, but they are similar in appearance, since they were formed under the same conditions. Prove the directional effect of natural selection.
Examples:
- wings of insects and birds;
- the front limbs of a mole and a bear;
- gills of polychaete worms, crustaceans and fish;
- tusks of walrus and elephant;
- thorns of cacti and hawthorn.
Rudiments are underdeveloped organs of modern organisms that were well developed in their ancestors.
Rudiments persist throughout life in all individuals of the species, but do not have much significance. They prove the relationship between organisms.
Examples:
- appendix, third eyelid, tailbone in humans;
- the rudiments of the bones of the hind limbs in whales;
- reduced eyes in moles;
- rudimentary wings in flightless birds;
- halteres in dipterans.
Atavisms are cases of returning to the traits of ancestors.
They arise in individual individuals of the species as developmental deviations. They prove that the genes of the ancestors responsible for the development of these traits have been preserved in the genotype of modern organisms.
Examples:
- excess hair, tail, multi-nipple in humans;
- three-toed limbs in a horse;
- legs of legless lizards and snakes.
