Biology Homework Help: Questions and Answers: Bats and humans are both mammals and share a common ancestor Because of this a human arm and a bat wing have similar bone structure. In contrast, bird wings and bat wings have different structures. Explain these relationships in terms of homologous and analogous structures.
Q1 Step by Step Answering: Homologous and Analogous Structures
- Homologous structures are traits inherited by two different organisms from a common ancestor. Despite different functions, they share similar underlying anatomy due to shared ancestry.
- In this case, a human arm and a bat wing are homologous structures because both humans and bats are mammals and share a common ancestor. The bone structure is similar, but the function differs (arms for grasping, wings for flying).
- Analogous structures, on the other hand, are traits that are similar due to similar environmental pressures, not common ancestry. These structures serve similar functions but differ in their anatomical structure.
- Bird wings and bat wings are analogous structures because although both enable flight, birds and bats do not share a recent common ancestor for this trait. Their wings evolved independently in response to the need for flight, but their underlying bone structures are different.
Q2. The Channel Islands are a series of small islands off the California coast. Each island has a genetically distinct population of foxes. Compare the population of foxes on one of these islands to the population of foxes in the forests of mainland California. Which is more likely to be impacted by genetic drift? Which is more likely to be at Hardy-Weinberg equilibrium?
Step by Step Answering: Genetic Drift and Hardy-Weinberg Equilibrium
- Genetic drift is more likely to impact foxes on the Channel Islands. This is because genetic drift tends to have a stronger effect in smaller populations, like those on the islands, where random changes in allele frequencies can occur more drastically. In contrast, mainland California foxes have a larger population, making them less susceptible to genetic drift.
- The population of foxes in mainland California is more likely to be at Hardy-Weinberg equilibrium. Hardy-Weinberg equilibrium assumes a large population with random mating, no mutations, no selection, and no migration, conditions that are more likely met by the larger mainland population than the isolated, smaller island populations.
Q3. Living organisms are commonly divided into six kingdoms: archaea, bacteria, fungi, protists, plants, and animals. What’s the biggest problem with classifying organisms in this way?
Step by Step Answering: Problems with Six Kingdom Classification
The biggest problem with classifying organisms into six kingdoms (archaea, bacteria, fungi, protists, plants, and animals) is that this system does not fully capture the complexity of evolutionary relationships. For instance:
- Protists represent a highly diverse group that doesn’t reflect a single evolutionary lineage; it includes organisms that are more closely related to plants, fungi, or animals than to each other.
- Archaea and bacteria are both prokaryotes but are very distinct at a molecular level. Archaea are often more closely related to eukaryotes than to bacteria, which isn’t well-represented by this kingdom system.
Modern classification based on phylogenetics (genetic relationships) often uses domains like Bacteria, Archaea, and Eukarya to better reflect these evolutionary distinctions.
Q4: Determining the Age of Rocks and Fossils
Step by Step Answering:
a. How Radioactive Elements Help Establish the Age of Rocks and Fossils
Radioactive elements decay at a predictable rate, measured as their half-life (the time it takes for half of the radioactive atoms to decay). By measuring the ratio of the original radioactive element to its decay products in rocks or fossils, scientists can estimate how much time has passed since the rock or fossil formed. This process, called radiometric dating, helps establish the age of ancient fossils and rocks.
b. How Index Fossils Help Establish the Age of Rocks and Fossils
Index fossils are fossils of organisms that lived during a relatively short, specific time period but were widespread geographically. These fossils help scientists correlate the age of rock layers.
- Fossils in the same layer as an index fossil are assumed to be roughly the same age.
- Fossils in lower layers of rock are older, as they were deposited earlier in Earth’s history.
- Fossils in higher layers of rock are younger because they were deposited more recently. Using index fossils allows scientists to establish a relative age of rocks and fossils, which can be correlated with radiometric dating for more precise age estimates.
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