Platyhelminthes Core Characteristics

These flashcards cover the core characteristics of Platyhelminthes, including their structure, systems, reproduction, classes, and specific examples.

Platyhelminthes

Flat worms (platy = flat, helminth = worm).

Bilateral symmetry

A type of symmetry where the organism can be divided into two equal halves.

Triploblastic

Having three tissue layers: ectoderm, mesoderm, endoderm.

Dorsoventrally flattened

A body shape that is flattened from top to bottom.

Unsegmented

Having no segments in the body structure.

Circulatory system in flatworms

Flatworms do not have a circulatory system; oxygen moves through the body by diffusion.

Diffusion in flatworms

Flatworms can rely on diffusion due to their thin bodies, allowing all cells to be close to the environment.

Incomplete gut

A digestive system with one opening where food enters and waste leaves.

Two-way gut

A type of gut where food enters and waste leaves through the same opening.

Cephalisation

The concentration of sensory organs and nerve tissue in the head.

Cerebral ganglion

The flatworm's 'brain', which is a concentration of nerve tissue.

Ladder-like nervous system

The shape of the flatworm nervous system, which resembles a ladder.

Ocelli

Light-sensitive eyespots found in flatworms.

Detection by ocelli

Ocelli detect the direction of light.

Diet of flatworms

Flatworms can be carnivores, predators, scavengers, or parasites.

Hermaphrodites

Organisms that have both male and female reproductive organs, like flatworms.

Copulation

The method by which flatworms reproduce sexually.

Transverse fission

A form of asexual reproduction where the flatworm splits into two.

Regeneration

The special ability of many flatworms to regrow lost body parts.

Turbellaria

The class that contains mostly free-living flatworms.

Parasitic flatworm classes

Monogenea, Trematoda, and Cestoda are classes of parasitic flatworms.

Cestoda

A class of flatworms commonly known as tapeworms.

Arthurdendyus triangulatus

The famous New Zealand flatworm species.

Impact of Arthurdendyus triangulatus in the UK

It kills large numbers of earthworms.