ACT science section does not depend on memorization but on how to extract the information. However, with a slight back ground on the various topics, it is easier to score the 35 or 36 in your coming test.
Natural Selection In ACT Science Section
Natural selection is a key mechanism of evolution proposed by Charles Darwin. It is the process through which species adapt to their environment over time, leading to the preservation of advantageous traits and the elimination of disadvantageous ones. This process is driven by several factors:
Variation: Within any population, there is genetic variation. Individuals within a species are not identical; they exhibit differences in traits such as size, color, speed, and resistance to diseases.
Competition: Resources in the environment are limited. This leads to competition among individuals for essentials like food, water, mates, and shelter.
Selection Pressure: Environmental factors exert pressure on populations. These factors can include predators, climate change, availability of food, and other challenges that influence the survival and reproduction of individuals.
Reproduction: Individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring. Over time, these advantageous traits become more common in the population.
Key Concepts in Natural Selection:
Survival of the Fittest: The phrase “survival of the fittest” is often used to describe natural selection. It means that individuals with traits best suited to their environment are more likely to survive, reproduce, and pass on their genes to the next generation.
Adaptation: Through natural selection, populations gradually evolve adaptations that help them survive in their specific environments. These adaptations can be structural, behavioral, or physiological.
Speciation: Over long periods of time, natural selection can lead to the formation of new species. When populations become isolated from one another and evolve different adaptations, they may eventually become distinct species.
Examples of Natural Selection:
Peppered Moths: The peppered moth in England is a classic example of natural selection. During the Industrial Revolution, pollution darkened the trees with soot. Dark moths became more common as they were better camouflaged against the darkened trees, while light-colored moths became easier targets for predators.
Darwin’s Finches: Darwin’s observations of finches on the Galápagos Islands showed how different beak shapes evolved in response to varying food sources. Finches with beaks suited to their specific diets were more successful in obtaining food and reproducing.
Types of Natural Selection:
Stabilizing Selection: In stabilizing selection, extreme phenotypes are selected against, leading to the preservation of intermediate phenotypes. This type of selection tends to maintain the status quo and is common in stable environments.
Directional Selection: In directional selection, one extreme phenotype is favored over the other, leading to a shift in the population towards that extreme. This type of selection occurs in response to changing environmental conditions.
Disruptive Selection: Disruptive selection favors extreme phenotypes over intermediate ones. This can lead to the divergence of a population into two distinct phenotypic groups, which may eventually result in the formation of separate species.
Genetic Drift and Natural Selection:
While natural selection is a powerful force in shaping populations, genetic drift is another factor that can influence the genetic makeup of a population. Genetic drift refers to random changes in allele frequencies due to chance events, especially in small populations. It can sometimes overwhelm the effects of natural selection, particularly in small or isolated populations.
Human Evolution and Natural Selection: evolution provides numerous examples of natural selection in action. Traits such as lactose tolerance in some populations, sickle cell anemia resistance in areas where malaria is prevalent, and adaptations to high-altitude environments are all products of natural selection acting on human populations.
Modern Applications of Natural Selection:
Antibiotic Resistance: The phenomenon of antibiotic resistance in bacteria is a clear example of natural selection at work. Bacteria that are resistant to antibiotics survive and reproduce, leading to the proliferation of resistant strains and making certain antibiotics less effective over time.
Pesticide Resistance: Similarly, in agriculture, pests can develop resistance to pesticides through natural selection. Pesticides kill susceptible individuals, leaving behind resistant ones to reproduce and pass on resistance genes to future generations.
Ongoing Research and Debate:
While natural selection is widely accepted as a central mechanism of evolution, ongoing research continues to deepen our understanding of its complexities. Concepts like sexual selection, gene flow, and epigenetics further contribute to our knowledge of how species evolve and adapt to their environments. By grasping these additional dimensions of natural selection and its implications across various organisms and contexts, you can develop a more comprehensive understanding of this foundational concept in biology and evolution.
Summary
Natural selection is a fundamental concept in biology that explains how species evolve and adapt to their environments over time. Understanding the principles of natural selection and its key mechanisms is crucial for interpreting scientific data and answering questions related to evolution on the ACT Science section.
Natural Selection- ACT Questions
A researcher is studying a population of birds in a particular region. The wingspan of the birds in the population has been gradually increasing over several generations. Which of the following statements best explains this change in wingspan?
A) Birds with longer wingspans are more likely to attract mates.
B) Longer wingspans allow birds to fly faster and escape predators more effectively.
C) Birds with longer wingspans have a higher rate of mutation.
D) The environment has changed, favoring birds with longer wingspans for survival.
Answer
Question 1:
- The wingspan of birds is increasing over generations.
- This indicates a change in the population due to environmental pressures.
Answer: D) The environment has changed, favoring birds with longer wingspans for survival.
This answer best aligns with the concept of natural selection, where a specific trait (longer wingspan) provides an advantage for survival and reproduction in a changing environment.
Question 2:
In a population of fish, there is a wide range of body sizes. Predators in the area tend to prey on smaller fish more easily. Over time, the average body size of the fish population has increased. Which of the following is the most likely explanation for this change?
A) Larger fish are more aggressive and dominate food sources.
B) Smaller fish have migrated to a different area.
C) Larger fish have an advantage in escaping predators.
D) Larger fish have a genetic advantage that allows them to survive and reproduce more effectively.
Answer
- Smaller fish are being preyed upon more frequently.
- The average body size of the fish population is increasing.
Answer: C) Larger fish have an advantage in escaping predators.
This option directly addresses the given scenario, where larger body size provides a survival advantage by making the fish less susceptible to predation.