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The diagram below represents some stages that occur in the formation of an embryo.
Which statement best describes stage X?*
The diagram below represents events that occur during sexual reproduction.
The stages labeled A, B, and C are necessary to ensure that the offspring will inherit*
The diagram below represents some stages in the process of development.
Stage 2 represents a cell that*
Which sequence best represents sexual reproduction?*
The inability of sperm cells to move normally could prevent the production of offspring by interfering with*
DNA replication occurs in preparation for*
The diagram below represents the processes leading to the formation of a human embryo.
The correct sequence for processes 1, 2, and 3 represented in the diagram is
A kitten was born with black fur and green eyes. The fur and eye color of its parents are shown in the chart below.
Which statement helps explain why the kitten has black fur?*
The diagram below summarizes some of the steps in the development of humans.
All the genetic information needed for the organism to develop is first present at*
Part of a process necessary for reproduction in complex organisms is represented below.
Step C results in the production of*
An alternative to the use of insecticides to combat the Mediterranean fruit fly is the Sterile Insect Technique (SIT). SIT involves the sterilization of male insects by radiation, which prevents the formation of functional male gametes. When these male insects mate with female insects of the same species, the result would be that*
A human cell that contains all of the information necessary for the growth and development of a complete organism is*
Base your answers to questions 13 on the passage below and on your knowledge of biology. Biologists have been studying the genes present in newborn twins.
Twins Don’t Share Everything
…Chemicals called epigenetic markers can be attached to those [inherited] genes, like flags or balloons hanging off the sides of the DNA ladder. These don’t just change the look of the genes. Like pieces of tape stuck over a light switch, these markers can force a gene to remain turned on or off. The type of marker scientists studied in the twins generally sticks the switch in the off position so that some proteins don’t get made. And that means the proteins’ jobs won’t get done.
Every time a cell divides, new epigenetic markers may form. Foods, pollutants, and stress may all contribute to the development of new markers. So throughout our lives we tend to accumulate more and more. But a few are there from the day we’re born.
…His [Jeffrey Craig’s] team found that newborn twins have markers attached to different genes from the very start. It’s true in identical twins, which come from the same fertilized egg. It’s also true in fraternal twins, which come from different fertilized eggs. However, fraternal twins had more such differences than identical twins did.
Source: Science News for Students; July 31, 2012
State one reason why identical twins should have fewer genetic differences than fraternal twins. *
All organisms need to reproduce for the continuation of their species. Discuss the process of reproduction in humans. In your answer, be sure to:
• identify one hormone present in a female that is involved in regulating the reproductive cycle 
• state one way the nucleus of a sex cell is different from the nucleus of a body cell 
• state how the normal chromosome number for humans is maintained from one generation to the next 
• identify one action by the mother that can influence the development of the embryo and state a result of that influence *
Base your answers to questions 18 on the information below and on your knowledge of biology.
The testes of a human male produce gametes. The process that produces these gametes differs from the process that produces new skin cells in the same individual.
Identify the type of cell division involved in each process.