SCIENCE 7: 3rd Marking Period: Growth, Development and Reproduction of Organisms --- CLASS NOTES3/14/2019
Gene
•Basic physical and functional unit of heredity •Made up of DNA •Each person has 2 copies of each gene, one inherited from each parent. DNA •Deoxyribonucleic Acid or DNA •Contains the instructions an organism needs to develop, live, and reproduce •Found inside every cell •Passed down from parents to children (offspring) Chromosomes •Thread-like molecules that carry heredity information •Made of protein and one molecule of DNA •Most have arranged pairs within the nucleus of the cell X/Y Chromosomes •Each person has one pair of sex chromosomes in each cell. •Females have two X chromosomes. •Males have an X and Y chromosome. •The Y chromosome contains a gene, which triggers embryonic development to become a male. Cell •Smallest structural, functional, and biological unit of all living organism •Often called the “building blocks of life” •Nucleus – organelle present in most eukaryotic cells – contains genetic material Asexual Reproduction •Type of reproduction by which offspring arise from a single organism •Produced by mitosis •Offspring inherit the genes of only one parent •The offspring is genetically identical (uniform)of the parent. Mitosis •Type of cell division •Results in two daughter cells having the same number and kind of chromosomes as the parent cell •Cell goes through different phases before becoming clones of parent Types of Asexual Reproduction •Binary Fission •Budding •Fragmentation •Regeneration •Vegetative Reproduction Binary Fission •Common in prokaryotes (organisms with no nucleus) •Occurs in some single-celled eukaryotes (with a nucleus) •Fully grown parent cell splits into two halves, producing two new cells •Examples: bacteria and amoeba, and euglena Budding •Offspring grows out of the body of the parent (buds) •Example: hydras Fragmentation •The body of the parent breaks into distinct pieces •Each piece can produce an offspring •Example: planarians Regeneration •If a piece of a parent is detached, it can grow and develop into a completely new offspring. •Example – some starfish Vegetative Reproduction •A process by which new organisms arise without production of seeds or spores •Example: some plants, potatoes Advantages of Asexual Reproduction •Good for organisms that are not mobile and cannot look for a mate •Numerous offspring without “costing” the parent great amount to energy •Quick Disadvantages of Asexual Reproduction •Lacks genetic variation •Because organisms are the same, they share the same weaknesses •If the environment changes, there may not be time to adapt quickly enough to survive. Sexual Reproduction •Type of reproduction by which offspring arise from two parents. •The testis in the male produces male gametes or sperm. •The ovary in the female produce female gametes or ovum. •Gametes (sex cells) are formed by meiosis. Meiosis •A type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. •Goes through many phases •Required to produce egg and sperm cells for sexual reproduction Mitosis vs Meiosis •Mitosis produces 2 diploid cells, which are identical to the parents. (uniform) •Meiosis produces 4 haploid cells, which contain some characteristics of the parent cell but are not identical. (diverse) Sexual Reproduction •A sperm enters an ova during fertilization. •Each gamete contains 23 pairs of chromosomes. •The two fuse to form a zygote with 46 pairs of chromosomes. •Offspring appearance vary due to new combinations of genes. •The zygote then divides by mitosis •It passes through different developmental phases to transform into a multicellular individual •The offspring are genetically different (not identical) to their parents Advantages of Sexual Reproduction •Leads to genetic variations in new generations, which is fundamental for environmental adaptation •Organism is more protected – does not necessarily have the weakness of parent •Removes bad genes from the population Disadvantages of Sexual Reproduction •Organism must find a mate •Takes longer time to reproduce •Can prevent favorable genes from being passed down •Produces fewer offspring Some Organisms Reproduce Both Ways •Some plants and animals can reproduce both ways •There are benefits to this adaptation. What might they be? •Plant examples: fungi, strawberries, daffodils •Animal examples: starlet sea anemone, jellyfish, sponges Mutations •A change that occurs in the DNA sequence •Causes changes in an organism – its appearance, how it behaves, and how it functions •Mutations are essential to evolution – the raw material of genetic variation Harmful Mutations •Sickle cell anemia •Cystic Fibrosis •Albinism •Wingless Fruit Fly •Hemophilia Mutations •Sickle cell anemia is a genetic disease with severe symptoms •Caused by a the mutation of the gene that helps make hemoglobin (carries O2 to red blood cells) •The “R” is the dominate gene and the “r” recessive
KOMODO DRAGONS:
http://www.nationalgeographic.com.au/videos/david-attenboroughs-natural-curiosities/no-male-needed-for-female-komodo-dragon-3218.aspx POLLINATION: https://www.sciencelearn.org.nz/resources/77-pollination-and-fertilisation |
Erik E. Mason
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