B2.3 Flashcards
Fossil Record
The collection of fossils identified from different periods of time that can be interpreted to form a hypothesis about the evolution of life on Earth.
Fossils
The preserved traces or remains of an organism which lived a very long time ago.
Evolution
The development of a new species over time through a process of natural selection.
Why is there no fossil record of the earliest cells?
Many organisms don’t get preserved because it is difficult to get the right conditions. Also, it is thought that many early organisms were soft tissue organisms and soft tissue doesn’t preserve, it just decays. The oldest fossils are thought to be so far into the ground that we haven’t dug that far so we can’t find them.
Why are there gaps in the fossil record?
Many organisms don’t get preserved because it is difficult to get the right conditions. Also, it is thought that many early organisms were soft tissue organisms and soft tissue doesn’t preserve, it just decays.
Pentadactyl
Five fingered.
Growth
Increase in size, length and mass, as well as increase in number of cells.
Elongation
Growth in one direction
What is the specific area where plant cells divide, elongate and differentiate into many types of cells called?
The meristem.
Differentiate
The process by which a less specialise cell becomes more specialised to perform a specific function. It often changes shape to achieve this.
Stem Cells
An unspecialised cell that can divide to produce more stem cells or different kinds of specialised cell.
What are the percentages for the composition of blood?
Plasma: 55%
White blood cells and platelets: <1%
Red blood cells: 45%
Red blood cells
Biconcave discs containing haemoglobin, that gives the blood its red colour, and carry oxygen around the body to tissues
White blood cells
Several different types of cells that are all part of the body’s defence system against disease.
Plasma
The liquid component of the blood that carries all the suspended cells and dissolved substances.
