Why Do We Have Different Seasons?

Educators will notice a natural progression of content spanning the earth and life sciences in this series of three clips using broad scientific data sets. Start off your unit with a hands-on, minds-on activity modeling the cause of the Earth’s seasons (Activity 1), using the video above as reinforcement. Then, explore the effect of the seasons on photosynthesis around the globe in a stunning time lapse. The last clip throws animals into the mix, layering onto this now-familiar map a data set of bird migration patterns.

The above clip serves as a helpful follow-up for a longer lesson that makes clear why the Earth has seasons. Get your students to stand up and use their own bodies in an active model! This kinesthetic activity demonstrates to students that the earth's tilt is what is responsible for shifting light patterns and the change in seasons. After your students have a more solid grasp of this traditionally confusing concept, use the above clip to review and reinforce their understanding.

Now that your students understand the reason for the seasons, extend the unit to explore the instrumental role the sun plays in fueling food webs, starting with producers. This clip illustrates the influence of the sun on the seasonal abundance of plant matter produced on land and in our oceans. How do plants respond to seasonal changes in sunlight? Which areas of land and oceans are most productive at different times of the year, and why?

Your class is now comfortable using patterns to identify cause and effect relationships. Can they extend this one level up the food chain to predators? In this visualization, you’ll see how seasonal changes drive patterns in animal behavior. Track the movement of two migratory birds of prey—ospreys and turkey vultures—as they travel between North and South America over a single calendar year. Assist your students to make connections as to how populations of organisms are dependent on the living things on which they prey.

Next Generation Science Standards Disciplinary Core Ideas for 3-Video Series

• ESS1.A: The Universe and Its Stars
  • (6-8) Patterns of the apparent motion of the sun, the moon, and stars in the sky can be observed, described, predicted, and explained with models.
     
• ESS1.B: Earth and the Solar System
  • (5) The orbits of Earth around the sun and of the moon around the Earth, together with the rotation of Earth about an axis between its North and South poles, cause observable patterns. These include day and night; daily changes in the length and direction of shadows; and different positions of the sun, moon, and stars at different times of the day, month, and year.
  • (6-8) Earth’s spin axis is fixed in direction over the short-term but tilted relative to its orbit around the sun. The seasons are a result of that tilt and are caused by the differential intensity of sunlight on different areas of Earth across the year.
     
• LS1.C: Organization for Matter and Energy Flow in Organisms
  • (6-8) Plants, algae (including phytoplankton), and many microorganisms use the energy from light to make sugars (food) from carbon dioxide from the atmosphere and water through the process of photosynthesis, which also releases oxygen.
  • (9-12) The process of photosynthesis converts light energy to stored chemical energy by converting carbon dioxide plus water into sugars plus released oxygen.
     
• LS2.A: Interdependent Relationships in Ecosystems:
  • (6-8) Organisms, and populations of organisms, are dependent on their environmental interactions both with other living things and with nonliving factors.
  • (6-8) In any ecosystem, organisms and populations with similar requirements for food, water, oxygen, or other resources may compete with each other for limited resources, access to which consequently constrains their growth and reproduction.
    ​
• PS3.D: Energy in Chemical Processes and Everyday Life:
  • ​(5) The energy released [from] food was once energy from the sun that was captured by plants in the chemical process that forms plant matter (from air and water).
  • (6-8) The chemical reaction by which plants produce complex food molecules (sugars) requires an energy input (i.e., from sunlight) to occur. In this reaction, carbon dioxide and water combine to form carbon-based organic molecules and release oxygen. Cellular respiration in plants and animals involve chemical reactions with oxygen that release stored energy. In these processes, complex molecules containing carbon react with oxygen to produce carbon dioxide and other materials.
  • (9-12) The main way that solar energy is captured and stored on Earth is through the complex chemical process known as photosynthesis.

California's Environmental Principles and Concepts

• Principle III: Natural systems proceed through cycles that humans depend upon, benefit from, and can alter.
  • Concept a: Students need to know that natural systems proceed through cycles and processes that are required for their functioning.

• carbon dioxide: a colorless, odorless gas that is present in the atmosphere, formed during respiration, produced during organic decomposition, used by plants in photosynthesis, and formed when any fuel containing carbon is burned
• orbit: the path described by one celestial body in its revolution about another
• orbital period: the time taken for a given object to make one complete orbit about another object; the Earth takes 365 days to orbit the sun.
• photosynthesis: the process by which a cell captures energy in sunlight and uses it to make food
• primary producer: an organism, such as a plant, that can make its own food

"The video about why we have different seasons is fantastic, and I will use it along with the Kinesthetic astronomy unit when I teach about the Sun-Earth system, why we have seasons, and how the sun drives the water cycle/ provides energy to drive seasons/ etc." -6th Grade Science Teacher from Stockton, CA

"I would love to use some of the videos and guiding questions as a way to provide connections to real-world phenomenon." -High School Life and Physical Science Student Teacher from Berkeley, CA

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Visualizations based on aggregated data provide the unique opportunity to engage your students in various Science Practices highlighted in the Next Generation Science Standards, including asking questions, analyzing and interpreting data, and constructing explanations. As an example, Academy educators developed sample activities such as this one and this one.

Astronomy Activities
You'd be surprised by how much astronomy you can learn with a light source, some painter's tape, and a can of play doh. This collection features nine of our most popular activities.

Why do we have seasons?
This NASA webpage addresses the misconception that the distance of the Earth and the Sun is the reason for the seasons and explains the Earth’s tilt is the true reason.

Seasons Interactive
This interactive will help students recognize the reason for the seasons as they manipulate time and the Earth’s tilt.

The Reason for the Seasons
This website gives background information of why we have seasons and visualizes the angle of sunlight one of the reason of the seasons.

Earth’s Orbit around the Sun
This Universe Update article provides background information on the orbital mechanics of the Earth-Sun system and how that contributes to why we have seasons.

Phytoplankton Bloom Imagery
NASA Modis

Land Productivity Data
NASA Modis Land Science Team, NASA Earth Observatory Team

Imagery
Reto Stockli

Ocean Productivity Data
Michael Behrenfeld, Professor Department of Botany and Plant Pathology, Oregon State University, www.science.oregonstate.edu/oceanproductivity

Earth Imagery
NASA Visible Earth