TARDIGRADES

Source: LiveScience

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Context

Detailed 3D images of the first tardigrade fossils ever discovered help scientists predict when tardigrades evolved their near-indestructibility — a trait that might have helped them survive multiple mass extinctions.

What Are Tardigrades?

• Tardigrades are commonly known as water bears or moss piglets.
• They are microscopic, aquatic animals that have the ability to survive some of the harshest conditions on Earth (extreme temperatures, radiation, and even the vacuum of space).
• These were discovered in 1773 by German zoologist Johann August Ephraim Goeze.
• They earned the nickname "little water bears" due to their resemblance to tiny, plump, segmented animals.
• There are around 1,300 known species of tardigrades.
• They range from 0.002 to 0.05 inches in size.

Habitat

• Tardigrades thrive in diverse environments, from oceans to droplets of water on plants.
• They can live in extreme locations such as the Himalayas and deep ocean trenches.

Diet

• Most tardigrades feed on plant cells, algae, and fungi by piercing the cells and sucking up their contents.
• Some species can consume smaller creatures, such as nematodes and rotifers.

Survival in Extreme Conditions

• This is primarily due to a unique survival strategy called cryptobiosis.
• In this state, they expel more than 95% of the water from their bodies, retract their head and legs, and curl into a dehydrated ball known as a tun.
• In this form, tardigrades nearly stop their metabolism.
• Tardigrades can remain in their tun state for decades, possibly even a century, before reviving once conditions become favorable again.
• Tardigrades produce unique proteins that protect their cells during cryptobiosis.
• When they expel water from their bodies, these proteins form a glass-like structure around the cells, ensuring protection until they can rehydrate.
• Tardigrades' ability to survive extreme conditions has allowed them to endure all five mass extinctions on Earth. Their resilience suggests they could outlive many other species, including humans.

Invertebrates

Category	Description
Definition	●Invertebrates are animals that lack a vertebral column (backbone or spine).
Characteristics	●Soft-bodied (some with exoskeletons) ● Diverse body structures and functions
Major Groups	●Arthropods (Insects, spiders, crabs) ●Mollusks (Snails, clams, octopuses) ●Annelids ●Cnidarians ●Echinoderms ●Nematodes
Habitat	●Found in nearly all environments: oceans, freshwater, terrestrial (land), and even extreme environments
Size Range	●From microscopic (e.g., rotifers) to several meters long (e.g., giant squid)
Respiratory System	●Varies by group: gills (e.g., mollusks), tracheae (e.g., insects), diffusion through the body surface
Circulatory System	●Open circulatory system (e.g., arthropods, mollusks) ●Closed circulatory system (e.g., annelids)
Nervous System	●Varies by group: simple nerve nets (e.g., cnidarians) to more complex systems with a brain (e.g., arthropods)
Symmetry	●Bilateral (e.g., arthropods, mollusks) ●Radial (e.g., echinoderms, cnidarians)
Importance	●Ecological roles (pollinators, decomposers) ●Source of food (e.g., seafood) ●Medical research

Sources:

LiveScience 

PRACTICE QUESTION Q:Consider the following: 1.Mussels 2.Clams 3.Squids Which of the above is/are invertebrates which can live both on land and in water? a)1 and 2 only b)2 and 3 only c)1 and 3 only d)1, 2 and 3 Answer: d Explanation: The molluscs (land and sea snails, squids and octopuses, mussels and clams), annelids (segmented worms) and arthropods (millipedes, scorpions, insects, crabs) represent the second major evolutionary branch of invertebrates. These phyla have both colonised aquatic habitats and successfully adapted to life on land.