Biology Quiz: Sponges, Cnidarians, and Arthropoda

Sponges

• Phylum Porifera
• Asymmetrical symmetry
• Two germ layers (diploblastic)
• Collar cells (choanocytes) - have flagella that beat to create water currents and filter food
• Spicules - structural support made of calcium carbonate or silica
  • Types: Calcareous spicules (calcium carbonate) and Siliceous spicules (silica)

Cnidarians

• Include jellyfish, sea anemones, and corals.
• Diploblastic
• Radial symmetry
• Nematocysts - stinging cells used for prey capture and defense
  • Harpoon-like structures that eject a toxin
• Two phases: Polyp and Medusa
  • Polyp stage: sessile and tubular, with a mouth and tentacles facing up
  • Medusa stage: free-floating, bell-shaped and with tentacles facing down

Phylum Arthropoda

• Includes insects and crustaceans
• Coelom: reduced, with a hemocoel

Alternation of Generations

• Gametophyte - haploid (n) stage, produces gametes (sperm and egg)
• Sporophyte - diploid (2n) stage, produces spores

Plant Life Cycles

• Mosses - Dominant stage is the gametophyte
• Ferns - Fronds are part of the sporophyte stage
• Pollen - male gametophyte, carries sperm to the egg

Plant Classifications

• Mosses - Nonvascular, no seeds, no flowers
• Ferns - Vascular, no seeds, no flowers
• Gymnosperms - Vascular, have seeds, no flowers
• Angiosperms - Vascular, have seeds, have flowers

Peach Fruit

• Simple fruit - develops from a single ovary
• Fleshy fruit - has a fleshy outer layer

Double Fertilization

• Two sperm involved in fertilization
• Sperm travels through the pollen tube
• Produces a 2n zygote (diploid embryo) and a 3n endosperm (triploid nutritive tissue)

Root Zones

• Zone 2 - Elongation Zone: Cells elongate, increasing root length
• Zone 3 - Maturation Zone: Cells differentiate into specific tissues
• Zone 4 - Root Hair Zone: Microscopic hairs increase surface area for water and nutrient absorption
• Area 5 - Root Cap: Protects the root tip as it grows through soil

Stem Structure

• Eudicot stem - vascular bundles arranged in a ring
• Monocot stem - vascular bundles scattered throughout the stem
• Vascular tissues:
  • Xylem - transports water and minerals up the stem
  • Phloem - transports sugars and other organic molecules throughout the plant

Root Types

• Taproot - single, thick main root, with smaller lateral roots (eudicots)
• Fibrous root - many thin roots branching out from the base of the stem (monocots)
• Eudicot root - vascular bundles arranged in a star shape
• Monocot root - vascular bundles scattered in a ring.

Sponges

• Sponges are in the phylum Porifera and have asymmetrical symmetry.
• Sponges have two germ layers.
• Collar cells (choanocytes) are specialized cells with a flagellum and a collar of microvilli. They create water currents for feeding and filter food particles.
• A spicule is a structural element found in sponges, providing support and protection.
• Sponge spicules can be made of calcium carbonate (calcareous spicules), silica (siliceous spicules), or spongin (protein fibers).

Cnidarians

• Cnidarians include jellyfish, corals, sea anemones, and hydroids.
• Cnidarians have two germ layers.
• Cnidarians have radial symmetry.
• Nematocysts are stinging cells used for prey capture and defense. When triggered, they release a barbed thread that injects toxins.
• Cnidarians exist in two phases during their life cycle: polyp (sessile) and medusa (free-floating).
• Phylum Cnidaria

Arthropods

• Insects and crustaceans belong to the phylum Arthropoda.
• Arthropods have a coelom, but it is reduced and filled with blood called hemolymph.

Alternation of Generations

• Gametophyte stage is haploid (n) and produces gametes by mitosis.
• Sporophyte stage is diploid (2n) and produces spores by meiosis.
• In mosses, the dominant and prevalent stage is the gametophyte.
• In ferns, the fronds are part of the sporophyte stage.
• Pollen is the male gametophyte in seed-bearing plants.

Plant Classifications

• Mosses are nonvascular, seedless, and flowerless.
• Ferns are vascular, seedless, and flowerless.
• Gymnosperms are vascular, seed-bearing, and flowerless.
• Angiosperms are vascular, seed-bearing, and flowering.

Fruits and Seeds

• A peach is a simple, fleshy fruit.

Double Fertilization

• Double fertilization is a process unique to flowering plants where two sperm are involved in fertilization.
• Pollen tube is a structure produced by pollen that carries sperm to the egg.
• Double fertilization results in the formation of a diploid (2n) zygote and a triploid (3n) endosperm.

Root Anatomy

• Root zone 2 contains the zone of elongation where cells lengthen.
• Root zone 3 is the zone of maturation where cells differentiate into specialized tissues.
• Root zone 4 is the root cap which protects the root tip as it grows through the soil.
• Root hairs are extensions of epidermal cells that increase surface area for water and nutrient absorption.
• Area 5 is the region of the root that is involved in the synthesis of hormones and root development.

Stem Anatomy

• A eudicot stem has vascular bundles arranged in a ring.
• Monocot stem has vascular bundles scattered throughout the stem.
• Vascular tissue includes xylem for water transport and phloem for sugar transport.

Root Types

• Tap root is a single, central root with smaller lateral roots that develops from a eudicot.
• Fibrous root is a system of many small, branching roots that develops from a monocot.
• A eudicot root has a central vascular cylinder surrounded by a cortex.
• A monocot root has a central vascular cylinder surrounded by a cortex, but the vascular tissues are arranged in a ring instead of a cylinder.