Biology Questions

during fetal development when is it possible to clearly hear the fetal heartbeat when the physician applies a stethoscope to the mothers abdomen

The events of the first week after fertilization are defined as

Mesenchyme surrounding cochlear duct differentiate into cartilage, which is induced by cochlear ductCartilage undergoes vacuolization and forms scala vestibuli and scala tympani

20. Artificial selection was used on corn to produce a single strain of corn with increased growth rates and greaterresistance to a fungus. Although farmers have continued to select for these traits, the productivity of this strain is nolonger increasing. This suggests that:A) the population size has been decreasing.B) artificial selection is not as strong as natural selection.C) the corn population has been weakened by artificial selection.D) all or most of the natural variation for these traits has been eliminated.E) long-term disruptive selection may lead to speciation.

Epithelium of cochlear duct forms inner ridge and outer ridgeThe outer ridge forms the organ of Corti including inner and outer rows of hair cells (with cilia) and covered by tectorial membrane

The layers of cells surrounding a human egg are collectively called the

Sperm require lots of energy and this is generated by mitochondria located within the

27. Brassica oleracea was a European wild plant. Early farmers were able to use artificial selection on this plant toproduce cabbage, Brussels sprouts, kohlrabi, kale, broccoli, and cauliflower. This diversification through selectionwas possible because:A) artificial selection is always possible, whereas natural selection requires much larger population sizes.B) the species contained large amounts of genetic variation.C) artificial selection does not require differential reproductive success, whereas natural selection does.D) exotic species are always more adaptable than the native species in an area.E) artificial selection is only done on plants that are used for food, whereas natural selection is used on all otherplants.

The Meckel's cartilage from first pharyngeal arch disappears except for two small portions at its dorsal ends. They form malleus and incus

Fusion of the linings from invagination of first pharyngeal arch and first pouch

It is derived from mesenchyme of first and second pharyngeal arches that flank (are in the side of) first pharyngeal cleft

Anotia (no external acoustic meatus)Microtia (small external ear)Preauricular appendagesPreauricular pit

during which stage of development does implantation occur, followed by initial development of the nervous system, limb buds and all other systems?

28. ______________ selection favors organisms that have character values at both extremes of the phenotypicdistribution.A) StabilizingB) DirectionalC) DisruptiveD) SexualE) Frequency-dependent

Otic vesicle outgrowth forms endolymphatic ductCentral portion of outpocketings of otic vesicle undergoes apoptosis to form semicircular ductsUtricle is also formed from vestibular region

Lateral part of cochlear duct attached to cartilage by spiral ligament Medial edge of cochear duct is attached to and supported by modiolus

29. Two populations of a species of frog live around the Gulf of Mexico. One population has a brown back and liveson rocky islands with brown rocks and little vegetation. A second population lives on the mainland among thevegetation and has a back that is speckled with greens and browns. This species is undergoing _______________selection.A) disruptiveB) stabilizingC) frequency-dependentD) sexualE) directional

During second month, three auditory hillocks (nodular masses of mesenchyme) take shape along each side of first pharyngeal cleft (six in total)The auditory hillocks enlarge asymmetrically and coalesce (come tgt) to form external ear

The 3 parts of sperm are the head, middle piece and

34. "Natural selection decreases genetic variability in a population." This statement is:A) always true.B) never true.C) sometimes true, especially in cases of stabilizing selection.D) sometimes true, especially in cases of disruptive selection.E) sometimes true, especially in cases of frequency-dependent selection.