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Std 10: Heredity and Evolution notes

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1. Complete the following diagram.   Ans)  a) Palaeontological b) Embryological Q.2. Read the following statements and justify the same in your own words with the help of suitable examples. a. Human evolution began approximately 7 crore years ago. Answer: The Earth's ice age began approximately 7 crore years ago. During this period, dinosaurs became extinct. Mammals started evolving and diversifying rapidly. Due to climatic changes, forest cover reduced significantly. The ancestors of monkey-like animals were Lemur-like animals that developed during this time. Around 4 crore years ago, these monkey-like animals gradually lost their tails. Their body size and brain capacity increased, leading to the evolution of ape-like mammals. These monkey-like ancestors shared evolutionary links with apes and human-like creatures. Human evolution was marked by an increase in brain size, the abili...
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Reproduction in lower and higher animakls

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  Human Reproduction Human Male Reproductive System The human male reproductive system consists of: Testes Accessory ducts Accessory glands External genitalia I. Primary Sex Organs – Testes a. Structure and Function Testes are a pair of primary sex organs. They are mesodermal in origin. Their main function is the production of sperms. b. Location Testes are located outside the abdominal cavity in a pouch called the scrotum . c. Development and Descent Testes develop in the abdominal cavity during early foetal life. Later, they descend into the scrotal sac through the inguinal canal . d. Suspension Testes are suspended in the scrotal sac by the spermatic cord . e. Attachment Testes are connected to the wall of the scrotum by a short fibromuscular band called the gubernaculum . f. Shape and Size Testes are oval in shape. Approximate size: Length: 4–5 cm Width: 2–3 cm g. Covering ...
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