KEY CONCEPT Animals are diverse but share common 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.
KEY CONCEPTAnimals are diverse but share common characteristics.
diploid parents produce diploid offspring
Diploid cells have two copies of each chromosome: one copy from the mother and one from the father
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.
fruit fly genes
Three criteria are used to categorize animals.
body plan symmetry
Animals with bilateral symmetry can be divided equally along only one plane, which splits an animal
into mirror-image sides.
Animals with radial symmetry have body parts arranged in a circle around a central axis.
Germ layer tissues are aligned in specific positions in an embryo and eventually give rise to all of an animal’s tissues and organs.
Endoderm-inner most layer, develops into the linings of the digestive tract and much of the respiratory system
Mesoderm-middle layer, gives rise to muscles and most internal organs
Ectoderm-outermost layer, gives rise to nervous system and skin
Simpler organisms with radial symmetry only have endoderm and ectoderm.
Acoelomates- have no coelom, or body cavity
Pseudocoelomates-have a false or partially lined body cavity with only 1 side being covered with mesoderm
Coelomates-have a true body cavity, both sides of the body cavity are lined with mesoderm
Protostomes and deuterostomes are the two major radiations on the animal phylogenetic tree.
jellyfish, coral, anemones
The current organization of the animal kingdom shows some unexpected relationships.