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Home Lớp 8 Khoa học tự nhiên 8 - sách Kết nối tri thức Bài 46: Cân bằng tự nhiênBài tập trung bình

{"common":{"save":0,"post_id":"9631","level":2,"total":10,"point":10,"point_extra":0},"segment":[{"id":"10498","post_id":"9631","mon_id":"1159539","chapter_id":"1160145","question":"M\u1ed9t qu\u1ea7n th\u1ec3 chu\u1ed9t \u0111\u1ed3ng có s\u1ed1 l\u01b0\u1ee3ng cá th\u1ec3 \u1edf các nhóm tu\u1ed5i nh\u01b0 sau:<\/p>- Nhóm tu\u1ed5i tr\u01b0\u1edbc sinh s\u1ea3n 44 con\/ha.<\/p>- Nhóm tu\u1ed5i sinh s\u1ea3n: 43 con\/ha<\/p>- Nhóm tu\u1ed5i sau sinh s\u1ea3n: 21 con\/ha<\/p>Bi\u1ec3u \u0111\u1ed3 tháp tu\u1ed5i c\u1ee7a qu\u1ea7n th\u1ec3 này \u0111ang \u1edf d\u1ea1ng nào?<\/p>","options":["A. D\u1ea1ng \u1ed5n \u0111\u1ecbnh","B. D\u1ea1ng phát tri\u1ec3n","C. D\u1ea1ng gi\u1ea3m sút","D. V\u1eeba \u1edf d\u1ea1ng \u1ed5n \u0111\u1ecbnh v\u1eeba \u1edf d\u1ea1ng phát tri\u1ec3n"],"correct":"2","level":"2","hint":"","answer":"\u0110áp án: B. D\u1ea1ng phát tri\u1ec3n<\/strong><\/p>Tháp tu\u1ed5i<\/strong> th\u1ec3 hi\u1ec7n c\u01a1 c\u1ea5u dân s\u1ed1 theo nhóm tu\u1ed5i c\u1ee7a m\u1ed9t qu\u1ea7n th\u1ec3. D\u1ef1a vào t\u1ec9 l\u1ec7 gi\u1eefa các nhóm tu\u1ed5i<\/strong>, ta có th\u1ec3 phân lo\u1ea1i:<\/p><ol data-end=\"551\" data-start=\"195\"> <li data-end=\"329\" data-start=\"195\">D\u1ea1ng phát tri\u1ec3n<\/strong>:<\/p> <ul data-end=\"329\" data-start=\"222\"> <li data-end=\"278\" data-start=\"222\">S\u1ed1 cá th\u1ec3 nhóm tu\u1ed5i tr\u01b0\u1edbc sinh s\u1ea3n > nhóm sinh s\u1ea3n<\/strong><\/p><\/li> <li data-end=\"329\" data-start=\"282\">→ D\u1ef1 báo t\u01b0\u01a1ng lai qu\u1ea7n th\u1ec3 s\u1ebd t\u0103ng nhanh<\/strong><\/p><\/li> <\/ul> <\/li> <li data-end=\"438\" data-start=\"331\">D\u1ea1ng \u1ed5n \u0111\u1ecbnh<\/strong>:<\/p> <ul data-end=\"438\" data-start=\"355\"> <li data-end=\"406\" data-start=\"355\">S\u1ed1 cá th\u1ec3 nhóm tr\u01b0\u1edbc sinh s\u1ea3n ≈ nhóm sinh s\u1ea3n<\/strong><\/p><\/li> <li data-end=\"438\" data-start=\"410\">→ Duy trì \u1ed5n \u0111\u1ecbnh s\u1ed1 l\u01b0\u1ee3ng<\/p><\/li> <\/ul> <\/li> <li data-end=\"551\" data-start=\"440\">D\u1ea1ng suy gi\u1ea3m<\/strong>:<\/p><\/li><\/ol>","type":"choose","extra_type":"classic","time":"0","user_id":"139","test":"0","date":"2025-07-07 22:57:41","option_type":"txt","len":2},{"id":"10499","post_id":"9631","mon_id":"1159539","chapter_id":"1160145","question":"M\u1ed9t qu\u1ea7n th\u1ec3 h\u01b0\u01a1u có s\u1ed1 l\u01b0\u1ee3ng cá th\u1ec3 \u1edf các nhóm tu\u1ed5i nh\u01b0 sau:<\/p>- Nhóm tu\u1ed5i tr\u01b0\u1edbc sinh s\u1ea3n: 25 con\/ha<\/p>- Nhóm tu\u1ed5i sinh s\u1ea3n: 45 con\/ha<\/p>- Nhóm tu\u1ed5i sau sinh s\u1ea3n: 15 con\/ha<\/p>Bi\u1ec3u \u0111\u1ed3 tháp tu\u1ed5i c\u1ee7a qu\u1ea7n th\u1ec3 này \u0111ang \u1edf d\u1ea1ng nào?<\/p>","options":["A. D\u1ea1ng phát tri\u1ec3n.","B. D\u1ea1ng \u1ed5n \u0111\u1ecbnh.","C. V\u1eeba \u1edf d\u1ea1ng \u1ed5n \u0111\u1ecbnh v\u1eeba \u1edf d\u1ea1ng phát tri\u1ec3n.","D. D\u1ea1ng gi\u1ea3m sút."],"correct":"2","level":"2","hint":"","answer":"\u0110áp án: B. D\u1ea1ng \u1ed5n \u0111\u1ecbnh.<\/strong><\/p><ul data-end=\"699\" data-start=\"415\"> <li data-end=\"494\" data-start=\"415\">Nhóm tr\u01b0\u1edbc sinh s\u1ea3n < nhóm \u0111ang sinh s\u1ea3n<\/strong> → không ph\u1ea3i d\u1ea1ng phát tri\u1ec3n<\/strong><\/p><\/li> <li data-end=\"619\" data-start=\"495\">Tuy nhiên<\/strong>, nhóm tr\u01b0\u1edbc sinh s\u1ea3n không quá th\u1ea5p<\/strong>, g\u1ea7n b\u1eb1ng 1\/2 nhóm sinh s\u1ea3n → duy trì qu\u1ea7n th\u1ec3 t\u01b0\u01a1ng \u0111\u1ed1i \u1ed5n \u0111\u1ecbnh<\/strong><\/p><\/li> <li data-end=\"699\" data-start=\"620\">Nhóm sau sinh s\u1ea3n ít<\/strong> → phù h\u1ee3p v\u1edbi c\u01a1 c\u1ea5u t\u1ef1 nhiên (vì tu\u1ed5i th\u1ecd th\u1ea5p h\u01a1n)<\/p><\/li><\/ul>\\nT\u1ec9 l\u1ec7 này phù h\u1ee3p v\u1edbi d\u1ea1ng \u1ed5n \u0111\u1ecbnh<\/strong>, ngh\u0129a là qu\u1ea7n th\u1ec3 có kh\u1ea3 n\u0103ng duy trì s\u1ed1 l\u01b0\u1ee3ng cá th\u1ec3 qua các th\u1ebf h\u1ec7<\/strong> mà không t\u0103ng\/gi\u1ea3m \u0111\u1ed9t ng\u1ed9t.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"139","test":"0","date":"2025-07-07 22:58:15","option_type":"txt","len":3},{"id":"10500","post_id":"9631","mon_id":"1159539","chapter_id":"1160145","question":"Trong qu\u1ea7n xã loài \u01b0u th\u1ebf là loài:<\/p>","options":["A. Có s\u1ed1 l\u01b0\u1ee3ng ít nh\u1ea5t trong qu\u1ea7n xã","B. Có s\u1ed1 l\u01b0\u1ee3ng nhi\u1ec1u trong qu\u1ea7n xã","C. Phân b\u1ed1 nhi\u1ec1u n\u01a1i trong qu\u1ea7n xã","D. Có vai trò quan tr\u1ecdng trong qu\u1ea7n xã"],"correct":"4","level":"2","hint":"","answer":"\u0110áp án: D. Có vai trò quan tr\u1ecdng trong qu\u1ea7n xã<\/strong><\/p>Loài \u01b0u th\u1ebf<\/strong> trong qu\u1ea7n xã là loài có \u1ea3nh h\u01b0\u1edfng l\u1edbn \u0111\u1ebfn các loài khác và \u0111\u1ebfn môi tr\u01b0\u1eddng s\u1ed1ng chung c\u1ee7a qu\u1ea7n xã<\/strong>, th\u01b0\u1eddng do:<\/p><ul data-end=\"394\" data-start=\"216\"> <li data-end=\"238\" data-start=\"216\">Có sinh kh\u1ed1i l\u1edbn<\/strong><\/p><\/li> <li data-end=\"264\" data-start=\"241\">Có ho\u1ea1t \u0111\u1ed9ng m\u1ea1nh<\/strong><\/p><\/li> <li data-end=\"336\" data-start=\"267\">Chi\u1ebfm \u01b0u th\u1ebf v\u1ec1 s\u1ed1 l\u01b0\u1ee3ng<\/strong> (nh\u01b0ng không b\u1eaft bu\u1ed9c ph\u1ea3i nhi\u1ec1u nh\u1ea5t)<\/p><\/li> <li data-end=\"394\" data-start=\"339\">Tác \u0111\u1ed9ng m\u1ea1nh \u0111\u1ebfn \u0111i\u1ec1u ki\u1ec7n sinh thái<\/strong> c\u1ee7a qu\u1ea7n xã<\/p><\/li><\/ul>","type":"choose","extra_type":"classic","time":"0","user_id":"139","test":"0","date":"2025-07-07 22:58:47","option_type":"txt","len":3}]}