Explanation

A protostome is an animal where the first opening that forms during embryonic development (the blastopore) becomes the mouth.

While the second opening develops into the anus. 

Explanation

As of the most widely accepted recent estimates, about 2.13 million species have been formally described by scientists.

This number includes:

• Animals (insects, mammals, birds, etc.)

• Plants

• Fungi

• Protists

• Bacteria and archaea (though many microbes remain undescribed)

Explanation

Parvoviruses are among the smallest DNA viruses, with a typical diameter of around 18–26 nanometers (nm).

So, 20 nm is the most accurate option from your list.

Explanation

The percentage of insect species out of all known organisms is approximately 53.1%,

While it's estimated that there are around 1.7 million known species, insects constitute over half of that number, with estimates suggesting around 900,000 species of insects. 

Explanation

The hypothalamus is a part of the brain that acts as the body's thermostat, regulating body temperature by adjusting heat production and heat loss to maintain a stable core temperature. 

Explanation

Actinopods are a group of protists that use specialized pseudopodia, called axopodia, for locomotion and capturing food. 

Explanation

Explanation

The ecological role of fungi as decomposers is primarily paralleled by bacteria.

Both fungi and bacteria are essential decomposers in ecosystems,

Breaking down dead organic matter and releasing nutrients back into the environment.

While fungi are known for their ability to decompose complex organic materials like cellulose and lignin

Bacteria also play a crucial role in breaking down a wide range of substances.

Together, they form the core of the decomposition process,

Which is vital for nutrient cycling and maintaining ecosystem health

Explanation

Spiral cleavage is characterized by diagonal cleavage planes that are not symmetrical between the poles, resulting in unequal blastomeres arranged in a spiral pattern.

Determinate cleavage means that the fate of each blastomere is predetermined early on, meaning each cell has a specific developmental role. 

Explanation

A marsupium, or pouch, is a specialized structure in marsupials (like kangaroos, koalas, and opossums)

where the young are carried and continue to develop after birth.

Rearing the young ones:

The pouch provides protection and warmth, ensuring the young can continue their development after birth.

Feeding the young ones:

The young have access to the mother's milk while in the pouch.