Evolution

What is the hypothesised structure of the first simple cells?

An RNA molecule enclosed in a vesicle of phospholipids

State the three rules Cell Theory

All living organisms are made up of one or more cells, cells are the basic units of life, all cells come from pre-existing cells by division

Describe some factors of an RNA molecule

Present in all living things and has the ability to carry genetic information

What are riboenzymes?

RNA molecules that catalyse reactions within cells

What’s one piece of evidence that suggests prokaryotic cells existed before eukaryotic cells?

Fossiled remains that have been found of prokaryotic cells pre-date the oldest eukaryotic cell fossils

How long has life existed on Earth?

Around 3.5 billion years, based on fossil evidence

What roles might RNA and ribozymes have played in early cells?

RNA stored genetic information and ribozymes catalysed reactions

Explain how the ancestry of most existing eukaryotic cells probably involved endosymbiotic events

Prokaryotes were engulfed by larger prokaryotes

Give some evidence for endosymbiosis

Mitochondria and chloroplasts have features similar to prokaryotes, such as their own circular DNA, ribosomes, and double membranes

What is comparative genomics?

The comparison of DNA between species to determine evolutionary relationships

How can the sequence of amino acids establish likely evolutionary relationships between organisms?

More closely related species have a greater number of similarities between the amino acid sequence of their proteins due to having fewer mutations in the DNA sequences

What does a phylogenetic tree show?

How species are related and how long ago they diverged from a common ancestor

How is a reproducing species defined?

Members can interbreed to produce fertile offspring

What are post‑zygotic isolating mechanisms?

The prevention of fertile hybrids, such as hybrid inviability (offspring dies) and hybrid sterility (offspring cannot reproduce)

How do human activities threaten species?

Over-hunting, habitat destruction, pollution, introduced species

What ethical responsibility do humans have?

To prevent species extinction and maintain biodiversity

What is a gene pool?

The sum of all the gene variations (alleles) of all the individuals in a population