TRILOBITES

Aspect

Details

Definition

●Trilobites are extinct marine arthropods that lived during the Paleozoic Era.

●They are one of the earliest-known groups of arthropods.

●Trilobites are the first animals known to have vision.

Time Period

●Existed from the Cambrian Period (~521 million years ago) to the end of the Permian Period (~252 million years ago).

Phylum

●Arthropoda (same as modern-day insects, crustaceans, and spiders)

Key Features

●Three-lobed body (hence the name "trilobite") divided into: head, body, tail.

●Exoskeleton made of chitin, providing protection.

●Segmentation: Flexible, allowing movement and adaptation to various habitats.

●Some trilobites had highly advanced compound eyes, with lenses made from calcite crystals.

Size Range

●Ranged from a few millimeters to over 70 cm in length.

Habitat

●Primarily marine organisms, living on or near the ocean floor.

●Some were benthic (lived on the seabed), while others were pelagic (swimming in the water column).

Diet

Varied diets: scavengers, predators, filter-feeders.

Category

Description

Characteristics

●Invertebrates with Exoskeleton, segmented bodies, jointed appendages, bilateral symmetry, open circulatory system.

●They make up about 75% of all animals on Earth.

Body Regions

Head, thorax, abdomen (some may have cephalothorax)

Key Classes

●Insects (largest group, 3 body parts, 6 legs)

●Arachnids (spiders, scorpions, 8 legs)

●Crustaceans(crabs, lobsters, 2-3 body parts, mostly aquatic)

●myriapods (including centipedes and millipedes).

Habitat

●Found in nearly all ecosystems: marine, freshwater, terrestrial

Significance

●Pollinators (bees), decomposers (termites), food source (crustaceans), pests (locusts), disease vectors (mosquitoes), ecological balance

Examples

●Ants, bees, spiders, crabs, lobsters, centipedes, butterflies

PRACTICE QUESTION

Q:Consider the following statements about Arthropods:

1. They do not contain blood.

2. In order to keep growing, they must go through stages of moulting.

Which of the above statements is/are correct?

a) 1 only

b) 2 only

c) Both 1 and 2

d) Neither 1 nor 2

Answer: c

Explanation:

1^st statement is correct:  Hemolymph is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which hemolymph cells called hemocytes are suspended.

2^nd statement is correct: Moulting, also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at specific times of the year, or at specific points in its life cycle.