Vocabulary of Concepts of Ch.20 Origin and evolution of life- II Bimester

angiosperm : Flowering plant.

2.       archaebacterium:Member of the prokaryotic domain Archaebacteria

3.       Archean eon :Eon in which life arose (3.8-2.5 bya).

4.       big bang :Model for origin of universe.

5.       Cenozoic era:The present era (65 mya to present).

6.       crust of Earth:Outer zone of low-density rocks resting on the Earth's mantle.

7.       dinosaur : One of a fabulous group of reptiles that originated in the Triassic and became the dominant land vertebrates for 125 million years.

8.       Ediacaran :One of the species with a highly flattened body that arose in the precambrian.

9.       endosymbiosis theory  Continuing physical contact between two species, one of which lives and reproduces inside the other's body.

10.   eubacterium :Prokaryotic cell; has a nucleoid, but no nucleus, cytoplasm, or cell membrane; most have a cell wall, some encapsulated.

11.   eukaryotic cell: Cell having a nucleus and other membrane-bound organelles.

12.   global broiling hypothesis :Theory that an asteroid impact caused the K-T mass extinction by creating a colossal fireball, the debris from which raised global air temperature by thousands of degrees.

13.   gymnosperm:Type of vascular plant in which seeds form on exposed surfaces of reproductive structures (e.g., on cone scales).

14.   K-T asteroid impact theory : A huge asteroid hit Earth at the K-T boundary; last dinosaurs perished during the mass extinction.

15.   mantle :Of mollusks, a tissue draped over the visceral mass. Of Earth, a zone of intermediatedensity rocks beneath the crust.

16.   Mesozoic era : An era (240-65 mya) of spectacular expansion in the range of global diversity.

17.   Paleozoic era :Era from Cambrian, Ordovician, Silurian, Devonian, Carboniferous, through the Permian (544 to 248 mya).

18.   prokaryotic cell : Archaebacterium or eubacterium; single-celled organism, most often walled; lacks the profusion of membranebound organelles observed in eukaryotic cells.

19.   Proterozoic eon: Period from 2.5 billion to 570 million years ago; period during which eukaryotic cells arose.

20.   protistan: Photoautotroph or heterotroph (or both) unlike bacteria; some like earliest eukaryotic cells. Has a nucleus, larger ribosomes, mitochondria, ER, Golgi bodies, chromosomes with numerous proteins, and cytoskeletal microtubules. 

21.   proto-cell: Hypothetic cell-like stage between chemical evolution and the first living cell.

22.   RNA world :One model for prebiotic evolution in which RNA was the template for protein synthesis before the evolution of DNA.

23.   stromatolite :Fossilized mats of shallow-water microbial communities, mainly cyanobacteria, from Archean to precambrian.