SPI Biology · Biodiversity and Classification

Plant and Animal Groups

Plants are grouped by whether they have tubes for water and whether they bear seeds; vertebrates are grouped into five classes by their skin, heart and breathing.

All Biodiversity and Classification notes

Why this matters

Two questions in the bank: one EASY (the group of horsetails and ferns) and one MODERATE (the animals with single circulation, named by their Latin genus names). The MODERATE one is won by knowing which genus is a fish, so learn the common examples by name.

Concept 1 of 2: The plant groups

Plants are sorted by three questions: does the body have a stem, root and leaves; does it have tubes (vascular tissue) to carry water; and does it make seeds, bare or inside a fruit?

Definition

Thallophyta (algae): no root, stem or leaves. Spirogyra, Chara.
Bryophyta (mosses, liverworts): no vascular tissue; the 'amphibians of the plant kingdom'. Funaria (moss), Marchantia (liverwort).
Pteridophyta: root, stem, leaves and vascular tissue, but no seeds (spores). Ferns, horsetails (Equisetum), Marsilea.
Gymnosperms: naked seeds, no fruit. Pine, cycas, deodar.
Angiosperms: seeds inside a fruit; flowering plants. Mango, wheat, rose.

Group	Vascular tissue	Seeds	Examples
Thallophyta	No	No	Spirogyra, Chara
Bryophyta	No	No	Funaria (moss), Marchantia
Pteridophyta	Yes	No (spores)	Ferns, horsetails, Marsilea First plants with vascular tissue, but still no seeds.
Gymnosperms	Yes	Naked	Pine, cycas
Angiosperms	Yes	Inside a fruit	Mango, wheat

Practice this conceptself-check · 4 quick reps

The same idea in a practice question:

Practice questionEasy

Example 1 · Biodiversity and Classification · Plant and Animal Groups

Horsetails and ferns belong to:

Ferns as mosses

Mosses (bryophytes) have no vascular tissue. Ferns and horsetails have it but bear no seeds, so they are pteridophytes.

Concept 2 of 2: The five vertebrate classes and their hearts

A fish's heart has two chambers and sends blood to the gills only, so blood passes through the heart once per round of the body: single circulation. Every other vertebrate sends blood through the heart twice. Questions often give Latin genus names, so learn which class each belongs to.

Definition

Pisces (fishes): gills, scales, two-chambered heart, single circulation. Labeo (rohu), Hippocampus (sea horse), Exocoetus (flying fish), Anabas (climbing perch).
Amphibia: moist skin, live on land and in water, three-chambered heart. Rana (frog), Hyla (tree frog), Salamander.
Reptilia: dry scaly skin, mostly three-chambered heart (crocodile has four). Draco (flying lizard), chameleon, turtle, snake.
Aves (birds): feathers, four-chambered heart. Pigeon, sparrow.
Mammalia: hair, mammary glands, four-chambered heart. Whale, dolphin, bat, human.

Class	Heart chambers	Circulation	Examples
Pisces	Two	Single	Labeo, Hippocampus, Exocoetus, Anabas Only the fishes have single circulation.
Amphibia	Three	Double	Rana, Hyla, Salamander
Reptilia	Three (crocodile four)	Double	Draco, chameleon, turtle
Aves	Four	Double	Pigeon, sparrow
Mammalia	Four	Double	Whale, dolphin, bat

Sea horse, flying fish and climbing perch are all true fishes; whale and dolphin are mammals.

Practice this conceptself-check · 4 quick reps

The same idea in a practice question:

Practice questionModerate

Example 2 · Biodiversity and Classification · Plant and Animal Groups

Single circulation i.e., blood flows through the heart only once during one cycle of passage through the body, is exhibited by

Whales and dolphins as fishes

Whales and dolphins live in water but breathe air with lungs and feed their young on milk: they are mammals with double circulation.

Sea horse and flying fish as not fish

The sea horse (Hippocampus) and flying fish (Exocoetus) look odd but have gills, fins and a two-chambered heart. They are true fishes.

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

Reference tables (2)

The plant groups5 rows

Group	Vascular tissue	Seeds	Examples
Thallophyta	No	No	Spirogyra, Chara
Bryophyta	No	No	Funaria (moss), Marchantia
Pteridophyta	Yes	No (spores)	Ferns, horsetails, Marsilea First plants with vascular tissue, but still no seeds.
Gymnosperms	Yes	Naked	Pine, cycas
Angiosperms	Yes	Inside a fruit	Mango, wheat

The five vertebrate classes and their hearts5 rows

Class	Heart chambers	Circulation	Examples
Pisces	Two	Single	Labeo, Hippocampus, Exocoetus, Anabas Only the fishes have single circulation.
Amphibia	Three	Double	Rana, Hyla, Salamander
Reptilia	Three (crocodile four)	Double	Draco, chameleon, turtle
Aves	Four	Double	Pigeon, sparrow
Mammalia	Four	Double	Whale, dolphin, bat

Sea horse, flying fish and climbing perch are all true fishes; whale and dolphin are mammals.

Watch out for (3)

Ferns as mosses
→ The plant groups
Whales and dolphins as fishes
→ The five vertebrate classes and their hearts
Sea horse and flying fish as not fish
→ The five vertebrate classes and their hearts

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