Evolution is a fundamental process that shapes the diversity of life on Earth. It is driven by several key factors that influence how species adapt and survive in their environments. This review sheet will explore the four primary factors contributing to evolution: the potential for population growth, genetic variation, competition for resources, and natural selection. Understanding these factors helps explain how species evolve and adapt over time.
Potential for a Species to Increase in Number: All species have the potential to reproduce and increase in number. However, not all offspring will survive to adulthood due to environmental constraints. This potential for population growth is a driving force behind evolution, as it creates the opportunity for natural selection to act on variations within the population.
Heritable Genetic Variation: Genetic variation arises from mutations and sexual reproduction. Mutations are random changes in DNA that can introduce new traits, while sexual reproduction shuffles genetic material, creating diverse combinations of traits. These variations are heritable, meaning they can be passed on to offspring and contribute to evolutionary change.
Competition for Limited Resources: Resources such as food, water, and shelter are limited in any environment. Organisms must compete for these resources to survive and reproduce. This competition influences which individuals are more successful in their environment and, consequently, which traits become more common in the population.
Proliferation of Better-Adapted Organisms: Organisms with traits that enhance their ability to survive and reproduce in a given environment are more likely to pass those traits on to the next generation. Over time, these advantageous traits become more prevalent in the population, leading to adaptation and evolutionary change.
NGSS Aligned Testing Question
Dinosaurs: Some Live and Some Die - Avian (bird-like) and non-avian dinosaurs in the northern hemisphere lived in extreme heat. The average summer temperature could range from 81° to 104°F. Winters were mild and wet, averaging around 59oF. There was no polar ice at this time. Most non-avian dinosaurs had a mass of about 7700 pounds. Most avian dinosaurs weighed significantly less and most mammals that coexisted with the dinosaurs weighed less than a pound.
A giant asteroid struck just off the coast of Mexico 66 million years ago. The asteroid impact event is referred to as the K-T extinction. Enormous amounts of dust, sulfur, and carbon dioxide entered the atmosphere. It caused Earth's average surface air temperatures to drop by as much as 47o F. Dust from the impact blocked the Sun’s radiation for an extended amount of time, and photosynthesis was drastically reduced. Many dinosaurs were immediately killed while others managed to survive for a period of time. All of the non-avian dinosaurs went extinct. The mammals that survived the impact increased in number. They continued to survive and evolve.
A possible explanation for why some organisms survived and others did not is that some were | |
---|---|
1 | herbivores that had a large variety of plants to eat |
2 | able to evolve quickly into better adapted non-avian species |
3 | better able to compete successfully after the asteroid impact |
4 | faster and stronger than others and were able to outrun the blast of the impact |
The potential for a species to increase in number provides a basis for natural selection. It creates a scenario where variation among individuals can be tested by the environment, leading to the selection of traits that improve survival and reproduction.
Heritable genetic variation introduces new traits into a population through mutations and sexual reproduction. This variation is passed on to offspring and provides the raw material for natural selection to act upon, leading to evolutionary changes.
Competition for limited resources drives natural selection by determining which individuals are more successful in their environment. Those with traits that enhance their ability to obtain resources and survive are more likely to reproduce and pass on their traits to the next generation.
The proliferation of better-adapted organisms means that traits which enhance survival and reproductive success become more common in the population. This process leads to adaptation, where species become better suited to their environment over time.
Mutations are changes in the DNA sequence that can introduce new traits into a population. These changes can be beneficial, neutral, or harmful, and they provide the genetic diversity needed for natural selection to act upon.
Sexual reproduction combines genetic material from two parents, resulting in offspring with unique combinations of traits. This shuffling of genes increases genetic variation within a population, providing more opportunities for natural selection to drive evolutionary change.
Mathematical models, such as distribution graphs and proportional reasoning, can help illustrate how evolutionary factors like genetic variation and competition influence population dynamics and trait frequencies over time.
Survival and reproduction are key factors in evolution. Organisms that are better adapted to their environment are more likely to survive, reproduce, and pass on their advantageous traits. Over time, these traits become more common in the population, leading to adaptation.
Not all offspring survive due to environmental constraints such as limited resources, predation, and competition. These factors create selective pressures that determine which individuals are more likely to survive and reproduce.
Evidence such as mathematical models, distribution graphs, and proportional reasoning can support claims about evolutionary factors. These tools help illustrate how genetic variation, competition, and survival contribute to evolutionary processes.
*continue your studies by accessing another review sheet below*
HS. Structure and Function: HS-LS1-1 : HS-LS1-2 : HS-LS1-3
HS. Matter and Energy in Organisms and Ecosystems: HS-LS1-5 : HS-LS1-6 : HS-LS1-7 : HS-LS2-3 : HS-LS2-4 : HS-LS2-5
HS. Interdependent Relationships in Ecosystems: HS-LS2-1 : HS-LS2-2 : HS-LS2-6 : HS-LS2-7 : HS-LS2-8
HS. Inheritance and Variation of Traits: HS-LS1-4 : HS-LS3-1 : HS-LS3-2 : HS-LS3-3 : HS-LS1-8
HS. Natural Selection and Evolution: HS-LS4-1 : HS-LS4-2 : HS-LS4-3 : HS-LS4-4 : HS-LS4-5
Disclaimer: The information provided is intended to serve as a study guide based on a contextual analysis of the NGSS standards for the Life Science Biology assessment. These study guides should be used as a supplement to your overall study strategy, and their alignment to the actual test format is not guaranteed. We recommend that you consult with your instructor for additional guidance on exam preparation.