A2 Evolution of Life

Question 1

Phyletic gradualism

Answer 1

model of evolution which states that most speciation is slow, uniform and gradual.

Question 2

Genes

Answer 2

sections of DNA that code for a protein. A gene is made up of two alleles, one from each parent, if the organism reproduces sexually.

Question 3

Adaptive radiation

Answer 3

a process when organisms diversify rapidly into many different forms, usually as a response to a change in the environment or to exploit a new ecological niche.

Question 4

Morphology

Answer 4

describes the shape of the organism.

Question 5

Benthonic

Answer 5

means living on the bottom of the sea or a river, maybe in the sediment or on top of it.

Question 6

Epifaunal

Answer 6

means living on top of the sediment or substrate.

Question 7

Substrate

Answer 7

the sediment or rock at the bottom of the sea.

Question 8

Pelagic

Answer 8

means floating in the water column, usually the open ocean.

Question 9

Nektonic

Answer 9

means actively swimming in the water column.

Question 10

Infaunal

Answer 10

means living in the sediment, maybe a burrower.

Question 11

Nematoblasts

Answer 11

stinging cells to drive away enemies or catch prey.

Question 12

Polyp

Answer 12

the soft-bodied part of the coral that sits inside the calice.

Question 13

Corallite

Answer 13

a cup-like calcareous skeleton of a single coral polyp.

Question 14

Bilateral symmetry

Answer 14

means one plane of symmetry, with two identical halves.

Question 15

Mural pores

Answer 15

connections between adjacent corallites, perhaps for communication.

Question 16

Radial symmetry

Answer 16

where many planes of symmetry can be seen.

Question 17

Corallum

Answer 17

the whole skeleton of a solitary or colonial coral.

Question 18

Extant

Answer 18

describes a species that still exists today.

Question 19

Symbiotic relationship

Answer 19

where two organisms live together for mutual benefit, neither of which can successfully live without the other.

Question 20

Zooxanthellae

Answer 20

a type of dinoflagellate (algae) that lives symbiotically inside modern coral polyps.

Question 21

Coral bleaching

Answer 21

occurs where a small increase in temperature (or pollution) causes the polyps to expel the algae within them and they die. This kills the reef and the dead corals look white.

Question 22

Strophic

Answer 22

means a straight hinge line. These are sometimes extended as ‘wings’.

Question 23

Astrophic

Answer 23

means the hinge line is not straight, may show a shallow or highly curved pattern. Sometimes known as non-strophic.

Question 24

Commisure

Answer 24

the margin between the valves at the posterior and may be curved, folded or zigzag.

Question 25

Fold and sulcus

Answer 25

a fold in the central or middle part of valves.

Question 26

Spatfall

Answer 26

the settling and attachment of juveniles to a substrate.

Question 27

Amphibian

Answer 27

a creature with two life styles, one in water, the other on land.

Question 28

Tetrapod

Answer 28

a creature with four limbs.

Question 29

Lobe-finned

Answer 29

fish that possessed both lungs and gills and had four fleshy fins supported by bones in a similar structure to a hand, e.g. lungfish.

Question 30

Terrestrial

Answer 30

describes anything relating to land.

Question 31

Swim bladder

Answer 31

a sac-like structure, which can be filled with gas or fluid, to control buoyancy in fish.

Question 32

Coelacanth

Answer 32

a fish from an ancient lineage, closely related to lungfish and reptiles. They were thought to be extinct since the end of the Cretaceous period, but are actually extant.

Question 33

Dinosaur

Answer 33

a Mesozoic reptile with an upright walking position or gait.

Question 34

Amniotic eggs

Answer 34

types of eggs with shells produced by birds and reptiles.

Question 35

Archosaurs

Answer 35

a group of reptiles dominating the Triassic. These were the ancestors of dinosaurs, birds and crocodiles.

Question 36

Pubis

Answer 36

the pubic bone.

Question 37

Ornithischia

Answer 37

one of the main divisions in dinosaur classification, in which two bones in the hip point backwards. This is the same as in birds, so they are known as ‘bird hipped’.

Question 38

Saurischia

Answer 38

one of the main divisions in dinosaur classification, in which one of the bones in the hip points forward. This is known as ‘reptile hipped’.

Question 39

Gastroliths

Answer 39

stones swallowed by animals which stay in the stomach and grind the food that they eat. This is usually alongside a gizzard, which is a lining inside the stomach to protect it from damage.

Question 40

Olfactory lobes

Answer 40

part of the brain that can process smell. The larger this area, the more acute the sense of smell.

Question 41

Coelurosaurs

Answer 41

a type of Theropod dinosaur, most closely related to birds.

Question 42

Dinobird

Answer 42

dinosaurs with feathers.

Question 43

Sternum

Answer 43

the breast bone.

Question 44

Furcula

Answer 44

a wishbone, a forked bone formed by fusing the collar bones (clavicles). This strengthens the skeleton to allow the birds to fly.

Question 45

Sexual dimorphism

Answer 45

means difference in size or appearance between the sexes of animals.