Question

Choose an animal which represents a particular phylum. Briefly describe its features characteristic of its phylum including morphology, embryology, and physiology. Identify adaptations of your animal compared with other animals. If you chose a more primitive animal, identify adaptations compared with more primitive organisms outside of the animal kingdom.

Answer 1

Arthropoda is a phylum of triploblastic, haemocoelomic, segmented invertebrates having head, thorax and abdomen, a chitinous exoskeleton and jointed legs and appendages. Some arthropods, like the insects, have legs with a single branch. The rest historically have legs with two branches (biramous appendages). The outer branch is often a flattened gill, while the inner branch is often used for walking or modified for grasping, chewing, or reproduction.

Apis is any bee member of the genus Apis, distinguished by the production and storage of honey and the construction of perennial, colonial nests from wax.

Anatomy Insects, like all arthropods, have no interior skeleton; instead, they have an exoskeleton, a hard outer layer made mostly of chitin which protects and supports the body. The insect body is divided into three parts the head, thorax, and abdomen The head is specialized for sensory input and food intake; the thorax, which is the anchor point for the legs and wings , is specialized for locomotion; and the abdomen for digestion, respiration excretion and reproduction. Although the general function of the three body regions is the same across all insect species, there are major differences in basic structure, with wings, legs, antennae, and mouthparts being highly variable from group to group.

Embryology

The size of the germ anlage varies relative to the length of the egg. The nuclei appear at the periphery to form a blastoderm that encompasses the whole surface of the egg. In metamorphic species honey bees, the germ anlage forms from virtually the entire blastoderm surface. The germ anlage forms from a comparatively small proportion of the blastoderm, called long-germ-type embryos, the complete body pattern (head, gnathal, thoracic, and abdominal) is ornate at the blastoderm stage and all segments become visible in development. Additional segments are added with time by proliferative growth. The pleisiomorphic form for insects is believed to be an midium-sized germ anlage. This germ embryogenesis is leading in direct-developing hemimetabolous insect. metamorphic insects exhibit long-germ development. Formation of the cellular blastoderm is followed by gastrulation, the process of cellular invigilation that results in the formation of a layered embryo comprising two germ layers. Segmentation proceeds closely simultaneously with gastrulation. gene activity that generates the segmental pattern of the embryo. segmentation proceeds by a progressive modification of positional information that will finally specify groups of cells that form metameric units. modification is initiated with maternally provided proteins that form gradients from the anterior to the posterior of the egg and early cleavage stages. Maternal proteins provide the coordinates the position of front and back of the embryo, The proteins encoded by the gap genes in turn activate the pair-rule genes. When pair-rule genes are absent, the larva has only half the normal number of segments. The pair-rule proteins then activate the segment polarity genes, a set of genes expressed in a segmen-tally reiterated manner. Finally, the homeotic genes are activated in a region-specific manner. The homeotic genes that are responsible for conferring segment character. They provide information on an individual segment will be a specific mouthpart, thoracic, or abdominal segment. the embryo grows, the germ band transforms from this essentially two-dimensional, two-layered sheet into a three-dimensional larva. Individual segments first become visible near the anterior end, where the ectoderm differentiates into the brain and compound eyes. Protrusions develop anterior to the mouth opening that will finally grow to form the labrum and the antennae. First three segments behind the mouth form paired appendages that become the mouthparts: mandibles, maxillae, and labium. The next three segments develop into the thorax and form appendages that become walking legs. During the remainder of embryogenesis, as organs develop and differentiate, both ectoderm and mesoderm, grow laterally and extend around the yolk. The two edges of the germ band meet and fuse along the dorsal mid-line, such that the mesodermal and ectodermal layers now enclose the yolk. embryogenesis involves the differentiation of the ectoderm and mesoderm into the organ systems of the larva or juvenile. The ectoderm gives rise to the bulk of the larval or adult form.

Physiology    digestion Honey bees have reversible movement of foods from mouthparts to/from a honey stomach. The proventriculus , honey stopper prevent nectar form entering The honey stomach is a crop or storage area to hold freshly collected nectar or water for transport to/from the nest. Digestion of foods occurs in the midgut. The hind-gut reclaims water and nutrients and passes small amounts of indigestible wastes to the rectum for storage until excretion. Unlike mammals the circulatory and respiratory systems are mostly separated .   The circulatory system is “open”, consisting of a dorsal heart and aorta to assist in blood circulation. The main functions of the circulatory system are to transport food from the midgut to body cells, transport gases, hormones, defensive proteins, waste materials from cells to excretory organs.Blood (hemolymph) has only a minor role in gas transport. Insects have no lungs or centralizediratory resp system of trachea which carry oxygen to and CO2 away from cells. Trachea are connected to the outside by a series of 10 holes in the exoskeleton called spiracles At rest respiration occurs passively by diffusion. Under stress, such as during flight, bees pump their abdomens to increase gas exchange and expand air sacs of the trachea. Though the blood contains no hemoglobin, muscles indirectly connected to the wings contain cytochrome, a molecule which enhances gas exchange. nervous system consists of the brain and 7 ganglia at various junctions throughout the body. Most locomotion is controlled by the ganglia not the brain. A beheaded insect can move it’s legs and wings vigorously. A decapitated bee can walk and sting but flying is not possible because it is out of balance without the head. The bee brain consists of a small bundle of cells with all the automatic functions transferred to the ganglia . The ganglia are reduced to barely visible proportions. Bees are able to learn and have “short-term” memory.

A honey bee has several different kinds of adaptations that help it to stay alive and perpetuate its species. A honey bee has structural and behavioral adaptations that protect itself and its relatives from danger. Some of the adaptations include its color, stinger and an ability to learn. the honey bee's adaptations consist of its yellow stripes and black body. These colors help the honey bee to blend in with the colors of flowers, which is helpful during pollination. The honey bee is protected from predators and attracted to flowers that may have some of the same hues as its own body. Honey bees often live near flowers and flower gardens. honey bee adaptation is its stinger. A honey bee only stings if it feels like it or its hive is being exposed. To protect its hive, a honey bee that uses its stinger will die and helps its relatives to survive. Honey bees also have behavioral adaptation, A honey bee learns how to pollinate and collect honey from its parents. It collect honey in the form of pollen sticks from flowers, flying the pollen back to its hive. The honey bee dance is a behavioral adaptation that attracts a honey bee to its mate.   

                                                                              The evolution of bee dances is an early masterpiece of tracing the evolution of complex behavioral traits. Three species of tropical honeybees and a variety of the honeybees' closest relatives, the stingless bees. dances of all species of the genus Apis consist of similar motor patterns, and the dances all contain information about distance and direction of a profitable food source. In all species, direction to a food source is assessed as the direction of the food source relative to the current position of the sun. In all species except the one considered most "primitive" (Apis florea) this angle is expressed during the dance as the angle relative to gravity