Evidence for Evolution Embryological factors

Evolution Fish Amphibian Phylogeny

Embryos of a variety of vertebrate classes are almost indistinguishable by their shape or by the formation of their head and eyes, their trunk, their limbs, and their tail (Fig. 2.8). For instance, during development, the germ cells of almost all vertebrates, including humans, go through an embryonic stage in which they bear a remarkable resemblance to a fish embryo. They form gill arches, even though they never develop a complete gill apparatus. This observation serves as evidence that the...

A A

Fig. 2.4a-c Autosomal dominant hereditary transmission (genotypes and pheno-types). A dominant inherited allele (character) A recessive inherited allele (character) AA homozygous affected Aa heterozygous affected aa homozygous healthy a One parent is heterozygous affected, one parent is homozygous healthy 50 of children are affected b Both parents are heterozygous affected 75 of children are affected c One parent is homozygous affected, one parent is homozygous healthy 100 of children are...

Smooth Muscle Tissue

Smooth muscle tissue is chiefly the muscle tissue of the intestines. It forms the greater part of the walls of the hollow viscera gastrointestinal tract, gallbladder, urinary tract, sex organs, blood vessels, etc. and is found in the distal respiratory tract, the eye, the hair, and the glands. Smooth muscle is controlled by the autonomic vegetative nervous system, but in many organs it can be stimulated by passive distension myo-genic stimulation . A smooth muscle cell is spindle-shaped, about...

Striated Muscle Tissue

Muscle Tissue Plants

Striated muscle tissue is divided into skeletal muscle tissue and cardiac muscle tissue. The very regular arrangement of the myofibrils and their subunits actin and myosin filaments in the individual muscle cells can be seen in the optical microscope as regular light and dark bands, which have given skeletal and cardiac muscle the name striated striped muscle Fig. 3.11b, c . This regular, striped arrangement of actin and my-osin filaments distinguishes striated muscle under the optic microscope...

The Nerves

Cross Section Mixed Nerve Bundle

Only the peripheral pathways are called nerves the pathways in the brain and spinal cord are not commonly called nerves, but rather tracts central pathways . One nerve contains several bundles of nerve fibers fasciculi Fig. 3.23a, b . A mixed nerve is one in which sensory afferent Fig. 3.23a, b Cross-section of a peripheral nerve a Overview b greatly magnified section of a Fig. 3.23a, b Cross-section of a peripheral nerve a Overview b greatly magnified section of a and motor efferent nerves run...