Class: Name: ( ) Date: 29 Evolution I 29.1 The origin of life (Book 4, p. 29-3) Scientists generally believe that the first organisms were formed by joining (1) molecules together. The organic molecules were produced from simple (2) substances present in the atmosphere of the early earth. 29.2 Evolution (Book 4, p. 29-5) At the present time, scientists generally accept the theory of (1) ( 進化 ), which suggests that life on earth started from a (2) ( 共同祖先 ). A Evidence for evolution: fossils (Book 4, p. 29-5) 1 Types of fossils (3) ( 化石 ) are the preserved remains or traces of ancient organisms. They can be divided into two types: - (4) ( 體化石 ): They include body parts of organisms They provide us with information on the (5) of ancient organisms and what they looked like. - (6) ( 遺跡化石 ): They include structures caused by the activity of organisms. They provide us with information on the (7) of ancient organisms. Classify the following fossils into body fossils and trace fossils: a b c dinosaur dung fossil dinosaur footprint shark tooth fossil d e f Body fossils: (8),, Trace fossils: (9),, fossilized burrows snail shell fossil dinosaur skull fossil (Second Edition) - 36 -
2 Formation of fossils One of the ways of fossil formation and how the fossils are exposed: 1 A fish dies. The soft parts of it decay, leaving the hard parts like the skeleton. The skeleton is then buried in mud and sand. 2 After millions of years, the mud and sand become rock due to great pressure from the upper layers of sediment ( 沉積物 ). Meanwhile, (10) begin to deposit in the fish skeleton and turn it into a fossil. mud and sand from river more recent mud and sand fish skeleton bottom of a lake rock fish skeleton becomes a fossil 3 (11) movement raises the rock above water. 4 Further earth movement or (12) exposes the fossil. younger rock layer fossil exposed older rock layer Other ways to preserve remains of organisms: - Small animals might get trapped in (13) ( 樹脂 ) secreted by trees. After a long time, resin turns into (14) ( 琥珀 ), preserving the animals inside. - Organisms can also be preserved in ice. 3 How a fossil record provides evidence for evolution The (15) of fossils in sedimentary rocks ( 沉積岩 ) forms the (16) ( 化石紀錄 ). - In sedimentary rocks, the (17) (uppermost / lowest) layer is the oldest rock containing the (18) (earliest / most recent) fossils. The fossil record agrees with the theory of evolution that: - existing life forms arose from (19) - life forms - organisms became more (20) in structure and more (21). (Second Edition) - 37 -
Scientists can now estimate the age of fossils by (22) ( 放射性同位素定年法 ). This helps scientists obtain information about the time of existence of organisms. Evolution of the horse: clues from the fossil record Time 60 million years ago 30 million years ago Today Bones of forelimb Body size 0.4 m 1 m 1.6 m - Body size of horses (23) over the past 60 million years. - The horse s legs became (24) over time. The number of toes was (25). Limitations of using fossil records as evidence for evolution: - There are (26) ( 缺少的環節 ) in fossil records. - (27) -bodied organisms usually do not form fossils. - The bodies of dead organisms may be eaten by other organisms or (28) before fossilization occurs. - The conditions in which the organisms died are not suitable for fossil formation. - Most fossils are (29) and may be damaged. - Some fossils are located in (30) areas. B Other evidence for evolution (Book 4, p. 29-12) 1 Homologous structures Some structures of different species may look very different and perform different functions, but their designs are basically the same. These structures are said to be (31) ( 同源的 ). (Second Edition) - 38 -
Example: The forelimbs of mammals (e.g. humans, horses, bats and whales) perform different functions, but all of them are (32) ( 五趾型肢 ). This suggests that these mammals evolved from a (33). Their limbs (34) to perform different functions in different environments. Identify to which mammal the following limbs belong. State the functions of the limbs. a b c d humerus ulna and radius carpals metacarpals and phalanges Mammal Bat Horse Human Whale Limb (a d) (35) (36) (37) (38) Function (39) (40) (41) (42) 2 Comparative biochemistry By comparing the similarity of certain chemicals (e.g. proteins and nucleic acids) in different species, the (43) relationship between them may be deduced. i) Comparing the amino acid sequence in proteins Scientists hold the view that the fewer the differences in the (44) sequence in the same type of protein of different species, the fewer the (45) which have occurred and the closer the phylogenetic relationship between the species. (Second Edition) - 39 -
Example: The difference in the amino acid sequence of one of the polypeptide chains of haemoglobin between humans and five other vertebrates: Vertebrate Gorilla Rhesus monkey Dog Chicken Frog Number of differences in amino acid sequence in haemoglobin between humans and other vertebrates 1 8 15 45 67 - Humans are (46) (more / less) closely related to gorillas than rhesus monkeys. - The evolutionary tree ( 進化樹 ) below shows the phylogenetic relationship between humans and the above five vertebrates. Identify vertebrates I to VI. I II III IV V VI I: human II: (47) III: (48) IV: (49) V: (50) ancestor VI: (51) ii) Comparing the base sequence of DNA The more similar the (52) sequence of DNA, the closer the phylogenetic relationship of the species. The similarity in the base sequence of DNA between humans and six other species of animals: Species Gorilla Rhesus monkey Chicken Mouse Rabbit Squirrel Similarity in base sequence of DNA between humans and other species 97.7% 91.1% 88% 85% 80% 75% - Humans have a (53) phylogenetic relationship with gorillas than rhesus monkeys. - This (54) (agrees / disagrees) with the findings when amino acid sequences in haemoglobin are compared. (Second Edition) - 40 -
Answers Ch 29 Evolution I 29.1 1 organic 2 inorganic 29.2 1 evolution 2 common ancestor 3 Fossils 4 Body fossils 5 existence 6 Trace fossils 7 activities 8 c, e, f 9 a, b, d 10 minerals 11 Earth 12 weathering 13 resin 14 amber 15 sequence 16 fossil record 17 lowest 18 earliest 19 pre-existing 20 complex 21 diversified 22 radioisotope dating 23 increased 24 longer 25 reduced 26 missing links 27 Soft 28 decay 29 incomplete 30 inaccessible 31 homologous 32 pentadactyl limbs 33 common ancestor 34 modified 35 c 36 b 37 a 38 d 39 flying 40 running 41 handling 42 swimming 43 phylogenetic 44 amino acid 45 mutations 46 more 47 gorilla 48 rhesus monkey 49 dog 50 chicken 51 frog 52 base 53 closer 54 agrees (Second Edition) - 41 -