Briefly describe the life cycle of an earthworm.
What will be an ideal response?
Copulation occurs between two earthworms that have both male and female reproductive tracts. They face belly to belly in opposite directions and are held together at their sticky clitellums. Sperm are transferred between them and are stored temporarily in their seminal receptacles. A few days after the individuals separate, each worm secretes a cocoon. The cocoon contains eggs and stored sperm. The eggs are fertilized and the cocoon slips off the front end of the worm and is deposited in the soil. In Lumbricus terrestis, a single young earthworm eats the other fertilized eggs. Late in development, it breaks free of the cocoon, becoming an adult in several weeks. As long as the stored sperm lasts, an earthworm will continue to form new cocoons.
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Through a microscope, paired chromosomes are visible within the nuclei of an unidentified cell sample. Which statement about these cells is true?
a. They cells have been damaged by prolonged dehydration and are beginning to die. b. The cells must be prokaryotes because eukaryotic nuclei are opaque to visible light. c. The cells were preparing to undergo cell division when the slide was prepared. d. The cells were collected from a patient suffering from acute celiac disease.
The letter “A” in the above figure represents
a. transverse. b. radial. c. tangential. d. elliptical. e. obtuse.
Which of the following statements about the human genome is false?
A: Protein coding regions make up less than 2% of the human genome sequence. B: Human genes generally have many large introns. C: Over 50% of the genome is comprised of transposons and other repetitive sequences. D: The human genome is unique in structure and composition when compared to any other organism.
The DQ is the _____ dose for irradiation of human cells.
a) single-target b) multi-hit c) lethal d) threshold