Sexual and Asexual Reproduction

Essential Questions:1. How are sexual and asexual reproduction comparable?2. What types of reproduction produces uniform and diverse offspring?3. How is genetic information passed from parents to offspring?4. What are the advantages and disadvantages of the two types of reproduction?5. What causes mutations and what are some examples?

Asexual Reproduction

Asexual Reproduction is a type of reproduction by which offspring arise from a single organism. New cells are produced by mitosis. Offspring inherit the genes of only one parent and is genetically identical to the parent.

Mitosis

Mitosis is a type of cell division, resulting 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

Binary Fission is common in prokaryotes (organisms with no nucleus). It occurs in some single-celled eukaryotes (with a nucleus). Fully grown parent cell splits into two halves, producing two new cells. Examples of organisms who use binary fission to replicate are bacteria and amoeba, and euglena.

Budding

In budding, offspring grows out of the body of the parent (buds). Examples are hydras.

Fragmentation

Fragmentation is when the body of the parent breaks into distinct pieces. Each piece can produce an offspring. Examples are planarians.

Regeneration

Regeneration happens if a piece of a parent is detached, it can grow and develop into a completely new offspring. An example – some starfish.

Vegetative Reproduction

Vegetative Reproduction is a process by which new organisms arise without production of seeds or spores. Example: some plants, potatoes.

Advantages of Asexual Reproduction

Asexual Reproduction in better because it is good for organisms that are not mobile and cannot look for a mate, numerous offspring without “costing” the parent great amount to energy, and it is quick.

Disadvantages of Asexual Reproduction

Disadvantages of asexual reproduction are it lacks genetic variation, because organisms are the same, they share the same weaknesses, and if the environment changes, there may not be time to adapt quickly enough to survive.

Sexual Reproduction

Sexual reproduction is the 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

Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. It goes through many phases and it is required to produce egg and sperm cells for sexual reproduction.

Mitosis vs Meiosis

Mitosis Meiosisproduces 2 diploid cells, which are identical to the parents. (uniform)

produces 4 haploid cells, which contain some characteristics of the parent cell but are not identical. (diverse)

Sexual Reproduction

During 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.

First stages of mitosis in a human embryo

Advantages of Sexual Reproduction

Advantages of sexual reproduction are that it leads to genetic variations in new generations, which is fundamental for environmental adaptation, the organism is more protected – does not necessarily have the weakness of parent, and it removes bad genes from the population.

Disadvantages of Sexual Reproduction

Disadvantages of sexual reproduction are that the organism must find a mate, it takes a longer time to reproduce, It can prevent favorable genes from being passed down, and it produces fewer offspring.

Some Organisms Reproduce Both Ways

Some plants and animals can reproduce both ways. There are huge benefits to this adaptation. Plant examples include fungi, strawberries, and daffodils. Animal examples include starlet sea anemone, jellyfish, and sponges.

Mutations

Mutations are changes that occurs in the DNA sequence. They cause changes in an organism – its appearance, how it behaves, and how it functions. Mutations are essential to evolution – the raw

material of genetic variation.There are several different types of mutations. Point

mutation is the change of one base in the DNA sequence.

Harmful Mutations

• Sickle cell anemia• Cystic Fibrosis• Albinism• Downs Syndrome• Wingless Fruit Fly• Hemophilia• Dwarfism