【Grade 7 Science】Let's Master the Classification of Living Things!

Hello everyone! Let's dive into the world of "Biological Classification" together.
There are so many plants and animals all around us. While they might look totally different at first glance, if we focus on their commonalities and differences, we can actually organize them into neat, logical groups.
You might be thinking, "That sounds like a lot to memorize," but don't worry! We'll break it down using familiar examples. Once you master this chapter, walks in the park and trips to the zoo will become so much more interesting!

1. Plant Classification: How do they reproduce?

Plants are broadly divided into two groups based on whether or not they produce "seeds" to reproduce.

① Seed Plants

These are plants that bloom flowers and produce seeds to create offspring. They are further divided into two groups based on where their "ovules" (the part that becomes the seed) are located.

  • Angiosperms: Plants where the ovule is enclosed inside an ovary. (Examples: Cherry blossoms, canola/rapeseed, azaleas)
  • Gymnosperms: Plants that lack an ovary, leaving the ovule exposed. (Examples: Pine, cedar, ginkgo, cycad)

【Pro Tip】
The Japanese term for Gymnosperm translates literally to "naked seed plant." The fact that the ovule is "exposed" or "naked" is their most defining feature!

② Further Classification of Angiosperms (Monocots and Dicots)

Angiosperms are further divided into two groups based on features like the number of leaves (cotyledons) that emerge when they sprout.

  • Dicots: Have 2 cotyledons. Their leaves have a net-like venation, and they have a taproot and lateral roots. (Examples: Canola, morning glory)
  • Monocots: Have 1 cotyledon. Their leaves have parallel venation, and they have fibrous roots. (Examples: Rice, corn, lilies)

【Study Hack: How to Remember】
Think of Monocots as being "sleek and straight!" Their leaves are long and narrow, their veins run straight and parallel, and their roots spread out like a beard (fibrous).

③ Plants that do not produce seeds

These plants reproduce using "spores" instead of seeds.

  • Ferns: Have clear distinctions between roots, stems, and leaves. (Examples: Japanese painted fern, bracken)
  • Mosses: Do not have clear distinctions between roots, stems, and leaves. They also lack vascular bundles (tubes for water transport). (Examples: Liverwort, hair cap moss)

【Common Mistake】
Mosses have root-like structures, but these are called "rhizoids." Their only job is to anchor the plant to the ground—they do not absorb water!

★ Summary for this section:
Plants can be classified by: "Do they make seeds? (Angiosperms vs. Gymnosperms)," "How many cotyledons? (Monocots vs. Dicots)," and "Do they reproduce with spores? (Ferns vs. Mosses)."

2. Animal Classification: Does it have a backbone?

Animals are broadly divided into two groups based on whether or not they have a "backbone" (spine).

① Vertebrates

Animals that have a backbone. They are categorized into five groups based on where they live and how they reproduce.

1. Fish: Breathe with gills, lay eggs in water. (Examples: Crucian carp, salmon)
2. Amphibians: Young breathe via gills/skin, adults breathe via lungs/skin. Lay shell-less eggs in water. (Examples: Frogs, newts)
3. Reptiles: Breathe with lungs, lay eggs with shells on land. (Examples: Snakes, lizards, turtles)
4. Birds: Breathe with lungs, lay eggs with shells. Maintain a constant body temperature (endotherms). (Examples: Sparrows, penguins)
5. Mammals: Breathe with lungs, give birth to live young (viviparity) after developing inside the mother. Raise young with milk. Endotherms. (Examples: Humans, dogs, whales)

【Key Concept: Ectotherms vs. Endotherms】
Animals whose body temperature changes with the environment are called "Ectotherms" (Fish, Amphibians, Reptiles).
Animals that can maintain a constant body temperature regardless of the environment are called "Endotherms" (Birds, Mammals).

【Tricky Examples】
A newt (imori) is an amphibian, while a gecko (yamori) is a reptile. Also, remember that whales and dolphins are mammals, not fish!

② Invertebrates

Animals without a backbone. Two groups are especially important for middle school science:

  • Arthropods: The body is covered by an exoskeleton, and they have jointed legs.
    • Insects (like beetles: 6 legs)
    • Crustaceans (like shrimp, crabs)
  • Mollusks: The body is soft and enclosed in a "mantle." (Examples: Clams, squid, octopus)

★ Summary for this section:
Always start by checking for a backbone! If it's a vertebrate, focus on "how they breathe," "how they lay eggs," and "their body temperature" to distinguish between the five groups.

Final Study Advice:

It might be tough to memorize all these names at first, but try turning it into a game! Whenever you see an animal or plant, ask yourself, "Is this an angiosperm?" or "Is this an ectotherm?"
In science, the fastest way to learn isn't just memorization—it's understanding the "rules of grouping" (classification criteria). Checking out a field guide or observing plants in your own neighborhood will make these concepts stick much better!

I'm cheering for you! Let's take it one step at a time!