Grade 10 Life Sciences: History of Life, Chemistry of Life, and Cytology

Fill-in-the-blank practice flashcards covering Grade 10 Life Sciences modules including the geological timescale, Cambrian explosion, mass extinctions, fossilisation, organic and inorganic chemistry of life, cell structure, and organelles.

Life on Earth originated in the oceans approximately __________ years ago.

$$3\,500\text{ million}$$

The most recent geological eon, which began approximately $500\text{ million}$ years ago, is the __________ eon.

Phanerozoic

The Phanerozoic eon is subdivided into three eras: the Paleozoic, Mesozoic, and __________ eras.

Cenozoic

Photosynthetic prokaryotes that began producing oxygen which accumulated in Earth's atmosphere about $2.7\text{ billion}$ years ago are called __________.

cyanobacteria

The Cambrian period began $543\text{ million}$ years ago, ended $505\text{ million}$ years ago, and lasted for __________ million years.

$$38$$

Following the Cambrian explosion, groups of animals evolved in the fossil record in the order of fish, amphibians, reptiles, birds, and finally __________.

mammals

The most severe mass extinction of all time occurred $252\text{ million}$ years ago during the __________ period due to volcanic eruptions.

Permian

Dinosaurs became extinct at the end of the Cretaceous period approximately __________ million years ago.

$$66$$

The process by which the remains of organisms are replaced by silica or calcium and turned into stone is called __________.

petrification

The method of dating that determines whether a fossil was formed before or after another fossil or geological event is called __________ dating.

relative

A fossil of an organism showing intermediate traits between two clearly defined stages of evolutionary development is known as a __________ fossil.

transitional

The mineral micronutrient that is an essential component of hemoglobin for transporting oxygen is __________.

iron (Fe)

A dietary deficiency of iodine in animals leads to impaired thyroid gland function and the deficiency disease known as __________.

goitre

The disaccharide sucrose is synthesized by chemically joining one molecule of glucose with one molecule of __________.

fructose

When testing a food solution for the presence of glucose using Benedict's solution, heating the mixture causes a colour change from blue to __________.

orange/brick red

A molecule of lipid is composed of one glycerol molecule linked to three __________ chains.

fatty acid

The medical condition characterised by the narrowing of arteries due to the formation of cholesterol plaques is called __________.

atherosclerosis

The monomers that link together via peptide bonds to form proteins are called __________.

amino acids

When high temperatures or extreme pH permanently disrupt the bonds holding a protein's active shape, the protein is said to be __________.

denatured

In the human body, metabolic enzymes function at an optimum temperature of __________.

$$37^\circ\text{C}$$

A deficiency in vitamin C leads to bleeding gums and bleeding under the skin, a condition known as __________.

scurvy

Openings in plant cell walls that contain strands of cytoplasm connecting adjacent plant cells are called __________.

plasmodesmata

The movement of water molecules across a selectively permeable membrane down a water potential gradient is known as __________.

osmosis

In the cell membrane shown in the diagram, each phospholipid molecule is composed of a hydrophilic head and a __________.

hydrophobic tail

In the mitochondrion shown below, the inner membrane folds inwards to create finger-like projections called __________.

cristae

Ribosomes that occur as free clusters within the cytoplasm are known as __________.

polyribosomes (or polysomes)

The organelle consisting of a stack of flattened sacs called cisternae that modifies and packages proteins into vesicles is the __________.

Golgi apparatus (or Golgi body)

In the chloroplast diagram shown below, individual stacks of disc-like thylakoids are known as __________.

grana (or a granum)

In the plant vacuole shown below, the selectively permeable single membrane surrounding the cell sap is the __________.

tonoplast

Plastids that are colourless and function primarily to store starch in plant cells are called __________.

leucoplasts

Unlike plant cells, animal cells lack a cell wall and plastids, but they possess an organelle called a __________.

centrosome