Explanation

The statement that Cycas have vessel elements in their xylem is incorrect.

Cycas, like other gymnosperms, do not have vessel elements; instead, they have tracheids for water conduction.

Vessel elements are a characteristic of angiosperms (flowering plants).

Cycas are gymnosperms and produce seeds, but they do not form flowers, and their leaves are typically pinnately compound.

Explanation

The body wall of sponges is composed of two main layers: the pinacoderm and the choanoderm.

The pinacoderm is the outermost layer, made up of flat cells called pinacocytes, which cover the external surface of the sponge.

Explanation

The nucleolus is the site within the nucleus where ribosomal RNA (rRNA) is synthesized and combined with proteins to form ribosome subunits.

Explanation

Gel electrophoresis is a technique used to separate DNA fragments based on their size by applying an electric field to a gel matrix.

Explanation

Promoter sites are specific DNA sequences where RNA polymerase binds to initiate transcription, the process of copying a gene's DNA sequence into RNA.

Explanation

Restriction enzymes are molecular scissors that cut DNA at specific sequences, a critical tool in molecular biology for gene cloning and DNA manipulation.

Explanation

The biogenetic law, also known as recapitulation theory, was proposed by Ernst Haeckel.

It suggests that the development of an organism (ontogeny) mirrors the evolutionary development of the species (phylogeny).

Explanation

Trilobites are an extinct group of marine arthropods that lived during the Paleozoic Era.

They are one of the earliest known groups of arthropods.

Explanation

The Paleozoic Era was a time of significant diversification of life, marked by the Cambrian Explosion, during which many major groups of animals first appeared in the fossil record.

Explanation

The mass extinction event that led to the demise of dinosaurs occurred at the end of the Cretaceous period, approximately 66 million years ago.