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23.1 Animal Characteristics
KEY CONCEPT
Animals are diverse but share common
characteristics.
23.1 Animal Characteristics
Animals are the most physically diverse kingdom of
organisms.
• Animals range in size from 25-meter-long blue whales
to microscopic rotifers.
• Animals are found nearly everywhere on Earth.
23.1 Animal Characteristics
All animals share a set of characteristics.
• All animals share a unique set of derived
characters.
• Animal cells are
supported by collagen.
– three-stranded
protein
– found in bone,
skin, ligaments,
fingernails,
and hair
23.1 Animal Characteristics
• Animals are diploid and usually reproduce sexually.
– diploid parents produce diploid offspring
– do not have free-living haploid life stages
Diploid cells have two copies of each chromosome:
one copy from the mother and one from the father
23.1 Animal Characteristics
• Most animals have Hox genes.
– Homeotic genes control early development.
– Hox genes determine the position of cells differentiation.
– A Hox gene mutation leads to the development of a body
structure in the wrong position.