Large pieces of food can be torn off by grygian bears or swallowed whole.
The fluid feeders suck fluid from their food source.
The hypotheses are not exclusive and there are three explanations at the same time.
The first plants invaded land around the same time as species proliferation.
At the same time, atmospheric and aquatic oxygen ance of land plants introduced a viable food source for any organ levels were increasing, permitting increased metabolic rates, isms that could utilize them.
The realm of land and air and an ozone layer had developed, blocking out harmful UV organisms presented with many challenges.
For colonization of land radiation and allowing complex life to thrive in shallow water, certain species evolved adaptations that prevented them and eventually on land.
Prey developed lung and internal fertilization features as new types of predator evolved.
The amniotic egg, which is a tough, protective shell, is a result of the develop enabling them to avoid their predators.
The proliferation of predator and prey types may have been a result of this evolutionary arms race.
During the Carboniferous period, about 300 mya, the amniotic egg appeared and was responsible for the success of the reptiles.
During the rise and fall of the dinosaurs, reptiles were to dominate the Earth.
Dinosaurs and mam mals appeared at the same time.
After the dinosaurs died out, the number and diversity of mammals exploded.
Choanoflagellates are believed to be the closest living relatives of animals.
Most biologists agree that the animal kingdom is monophy shows many different types of life, some of which are now extinct.
Scientists recognize 35 animal phyla today.
The first simple animals may have arisen when some of these related to one another, such as chordates and jellyfish, became specialized functions.
Carefully examining body features and cells.
Evolutionary biologists have been able to propose models for complex body plans found in modern animals because of the changes that have been made to this more recently.
The monophyletic nature of the animal kingdom in mind, scien ally classified animal diversity in terms of three main morphological tists have attempted to identify the species from which most and developmental features of animal body plans The closest living relative is 1.
The choanoflagellate is a type of body symmetry.
A single flagellum surrounds a number of germ layers.
The features of the embryonic development collar are shown in Figure 28.21b.
We will discuss the major features of animal body plans.
Next, scientists theorize.
About 35 different animals have been identified by biologists.
In the next two chapters, we will discuss the 13 most abundant and recognizable phyla.
The first animals evolved from a choanoflagellate-like ancestor.
The ability to move the proportions of the body on either side of a median plane is correlated with the existence of bal Bilateral symmetry.
The sory structures at the anterior end of the body were asymmetric.
The animals are dangerous.
Most animals are symmetrical.
The formation of a hollow ball of cells called the blastula is the result of cleavage.
The cells lining the archenteron become the endoderm in the gastrula.
The blastula has cells on the outside.
The middle layer of the Bilateria is called the mesoderm.
There are animals that do not form aderm.
Look back to figure 25.8.
The archenteron opens to the outside.
The Bilateria develop a third layer of cells from a secondary opening if an anus is formed.
The top view has turned into a mouth.
The person becomes anus.
The blastopore becomes the mouth in Protostomes.
The blastopore becomes anus in deuterostomes.
Deuterostomes have indeterminate cleavage, whereas Protostomes have determinate cleavage.
All deuterostomes have radial cleavage.
The direction of the cleavage is indicated by dashed arrows.
When one cell is excised from a four-cell sea urchin embryo, both the single cell and the remaining three can form viable embryos.