Question

1.What describes the metabolism of an animal that can maintain a homeostatic internal temperature using physiological feedback processes

2.Describe the structure of the four embryological features that are unique to the Phylum Chordata and that distinguish chordates from all other animal phyla

3.When a sexually reproducing population undergoes speciation, whereby the new species use different types of social behaviors to attract mates, the speciation event is generally resulting from some type of ___________ isolation mechanism.

4.What term describes a spontaneous alternation in the arrangement of nucleotides within a germ line chromosome that can result in either a structural or physiological change in future generations

Answer 1

1 Thermoregulation

Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. It includes all phenomena in which an organism maintains a mean or variance of body temperature that deviates from a null expectation, defined by random use of thermal microclimates and passive exchange of heat with the environment.

Mechanisms of thermoregulation

Animals can be divided into endotherms and ectotherms based on their temperature regulation.Endotherms, such as birds and mammals, use metabolic heat to maintain a stable internal temperature, often one different from the environment.

Ectotherms, like lizards and snakes, do not use metabolic heat to maintain their body temperature but take on the temperature of the environment. Both endotherms and ectotherms have adaptations features that arose by natural selection that help them maintain a healthy body temperature. These adaptations can be behavioral, anatomical, or physiological. Some adaptations increase heat production in endotherms when it’s cold. Others, in both endotherms and ectotherms, increase or decrease exchange of heat with the environment

2. The four distinctive characteristics that, taken together, set chordates apart form all other phyla are the notochord; single, dorsal,hollow nerve cord; pharyngeal slits; and postanal tail. These characteristics are always found at some embryonic stage, although they may be altered or may disappear altogether in later stages of the life cycle. (See the image)

Notochord :

which is a flexible, rod-shaped structure that is found in the embryonic stage of all chordates and in the adult stage of some chordate species. It is located between the digestive tube and the nerve cord, and provides skeletal support through the length of the body. In some chordates, the notochord acts as the primary axial support of the body throughout the animal’s lifetime. In vertebrates, the notochord is present during embryonic development, at which time it induces the development of the neural tube and serves as a support for the developing embryonic body. The notochord, however, is not found in the postnatal stage of vertebrates; at this point, it has been replaced by the vertebral column (that is, the spine).

Dorsal hollow nerve cord :

It derives from ectoderm that rolls into a hollow tube during development. In chordates, it is located dorsal to the notochord. In contrast, other animal phyla are characterized by solid nerve cords that are located either ventrally or laterally. The nerve cord found in most chordate embryos develops into the brain and spinal cord, which compose the central nervous system.

Pharyngeal slits :

They are openings in the pharynx (the region just posterior to the mouth) that extend to the outside environment. In organisms that live in aquatic environments, pharyngeal slits allow for the exit of water that enters the mouth during feeding. Some invertebrate chordates use the pharyngeal slits to filter food out of the water that enters the mouth. In vertebrate fishes, the pharyngeal slits are modified into gill supports, and in jawed fishes, into jaw supports. In tetrapods, the slits are modified into components of the ear and tonsils.

post anal tail :

is a posterior elongation of the body, extending beyond the anus. The tail contains skeletal elements and muscles, which provide a source of locomotion in aquatic species, such as fishes. In some terrestrial vertebrates, the tail also helps with balance, courting, and signaling when danger is near. In humans, the post-anal tail is vestigial, that is, reduced in size and nonfunctional.

The distinguishing characters of Phylum Chordata with other phyla

*They are bilaterally symmetrical and triploblastic.

*Chordates are coelomate and show an organ system level of organisation.

*They have the characteristic notochord, dorsal nerve cord, pharyngeal slits.

*Also, they have a post-anal

*In this phylum, the nervous system is dorsal, hollow and single.

The heart is ventral, with a closed circulatory system.

*The habitat of these animals is widespread. So we can find them in the marine environment, fresh waters as well as terrestrial environments

3. reproductive isolation

It is the inability of a species to breed successfully with related species due to geographical, behavioral, physiological, or genetic barriers or differences.

The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offspring are sterile. These barriers maintain the integrity of a species by reducing gene flow between related species.

4. Mutation

Mutations are heritable changes in genotype that can occur spontaneously or be induced by chemical or physical treatments. Mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke etc.