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9th, 10th, 11th, 12th


Science, Biology

Resource Type

  • Videos, 4 minutes, 54 seconds, CC, Subtitles

Regional Focus



YouTube Video

Why Some Animals Are Shrinking

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  • This video provides evidence to show that animals are shrinking in a warmer climate. Evidence includes graphs and pictures with changes in bird size over the past 40 years and references to articles that discuss shrinking amphibians and mammals. 
  • The video also describes the consequences of changing animal sizes. Animals may not be able to migrate as far, they may have fewer offspring, and there can be major ecological consequences as interspecific relationships change. 
  • While not all animals may shrink, and some may even grow large, the physiology, ecology, and consequences of these changes is examined and explained. The mechanisms of selection pressure and developmental plasticity are explained.
Teaching Tips


  • The video is concise and provides evidence and great visuals for an interesting consequence of a warming climate to animals.
  • The video provides an excellent background for individuals who would like to broadly study climate change consequences to animals.

Additional Prerequisites

  • Students should be familiar with the concepts of climate change, adaptation, and natural selection.


Scientist Notes
This resource is a 5-minute video that looks at a recently discovered phenomenon - many animal species are shrinking in size - and examines some potential causes. The primary driver seems to be increasing temperatures due to climate change, which plays out differently in birds and mammals than it does for amphibians. This resource is recommended for teaching.
  • Science and Engineering
    • LS2: Ecosystems: Interactions, Energy, and Dynamics
      • HS-LS2-6 Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem.
    • LS4: Biological Evolution: Unity and Diversity
      • HS-LS4-4 Construct an explanation based on evidence for how natural selection leads to adaptation of populations.
      • HS-LS4-5 Evaluate the evidence supporting claims that changes in environmental conditions may result in: (1) increases in the number of individuals of some species, (2) the emergence of new species over time, and (3) the extinction of other species.
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