Tutor profile: Abigail J.
Differentiate between homologous, analogous, and vestigial structures and why they are evidence of evolution.
A homologous structure is a feature that is similar in structure but may have different functions in different organisms. For example, the forearm bones of a cat and a human are very similar, however they serve different functions. This suggests that humans and cats have a distant common ancestor. Analogous structures are features that have similar functions but different structures. An example would be a bird wing and a butterfly wing. Both have evolved to give the organism the ability to fly, however the structures are not similar. This suggests that there is not a distant common ancestor, but that the ancestors of these organisms developed this adaptation to survive in their environments. Lastly, a vestigial structure is a feature that is a remnant of an organ that had a function in an early ancestor. An example would be the pelvis of whales. Whales today do not need a pelvis as they do not have hind legs, however a distant ancestor of whales did have hind legs. The presence of the pelvis in whales suggests that over time the organism adapted to life in the ocean and gave rise to the many species of whale today.
How would a teacher use formative and summative assessment to reflect on their teaching?
There are many different forms of formative assessment that can be used to determine where students are struggling and excelling in the subject matter. Examples of formative assessment can be a quiz, exit ticket, whole class review game, lab activity, or even just a question asked during class. The teacher can use student scores, responses, and execution of labs or other activities to gauge student understanding. If many students have a similar misconception or get the same question wrong, the teacher can go back and reteach. They will often use a different strategy than was used originally before moving on to a new or more complex topic. At this point, a teacher can reflect on the original lesson and make adjustments as needed, or even scrap that method and try something else altogether. A summative assessment such as a test or end of chapter/class project would let the teacher know if the students were able to connect the concepts and apply their understanding. Again, the teacher can gauge student progress and reflect. They might consider the original lessons taught, if the test was fair and tested for what the teacher intended, or the clarity of the project instructions, and make adjustments accordingly.
Explain, using examples, how the human body uses negative feedback mechanisms to maintain homeostasis.
The body uses negative feedback mechanisms to bring certain internal conditions back to a "set-point." For example, if the body temperature drops below 98.6 degrees F (37 C), the hypothalamus senses this. The nervous system then signals dermal blood vessels to constrict and sweat glands to become inactive. This allows more blood to keep vital organs warm and stops any heat loss by evaporative cooling. If body temperature continues to drop, the nervous system will signal muscles to involuntarily contract which produces heat. This is what we know as shivering. This will continue until normal body temperature is restored. If body temperature rises above normal, the opposite will happen. The hypothalamus will sense an increase in temperature and signal the nervous system to dilate dermal blood vessels and activate sweat glands. This will cause the body's temperature to decrease.
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