Plant and Animal Sexual Reproduction Notes PDF

Biology 2 SEXUAL REPRODUCTION IN PLANTS AND ANIMALS  Lesson Objectives: Explain how plants and animals differ in terms of sexual reproduction ARE YOU READY? Sexual reproduction requires two parents, each contribute a gamete that contains haploid number of chromosomes. When these two ga...

Biology 2 SEXUAL REPRODUCTION IN PLANTS AND ANIMALS  Lesson Objectives: Explain how plants and animals differ in terms of sexual reproduction ARE YOU READY? Sexual reproduction requires two parents, each contribute a gamete that contains haploid number of chromosomes. When these two gametes (egg and sperm) unite during fertilization, the fertilized egg becomes a zygote. The zygote continues to develop into an embryo until it becomes a full-grown new individual.  The new organism resulting from sexual reproduction is genetically different in as much as the new set of genes are combined traits from both parents. Asexual reproduction requires only one parent. Since the offspring is not a product of fertilization, its genetic make-up is exactly a carbon copy from the parent.  In animals, such reproductive processes are observed primarily in unicellular organisms such as bacteria, protozoans, and some fungi. Identify the types of reproduction in the following images. ARE YOU READY?  Plants reproduce sexually either by two processes: unisexual or bisexual. Unisexual flowers contain male and female reproductive organs in separate flowers. Bisexual flowers contain both male and female reproductive organs in the same flower. Flowers are the reproductive structures of angiosperms (seed bearing plants).  Flowering plants reproduce sexually through a process called pollination. The flowers contain male sex organs called stamens and female sex organs called pistils. The anther is the part of the stamen that contains pollen.  Self-pollination happens when a plant’s own pollen fertilizes its own ovules. Cross pollination happens when the wind or some insects transfer pollens from one plant to fertilize the ovules of another plant. The advantage of cross pollination is that it promotes genetic diversity.  The union of a pollen and the ovum during fertilization results in the formation of a seed. The seed contains the seed coat, embryo and the endosperm. The embryo is the young plant before it emerges from the seed. The endosperm supplies food and nutrient for the embryo to grow.  In most cases (except, apomixis) sexual reproduction in plants involves the union of male gamete present in the pollens and female gamete (egg) present in the ovary of a flower. Both gametes reproduce by meiosis. Each gamete contains haploid number of chromosomes. When fertilization occurs the two haploid chromosomes fuses resulting to the formation of an embryo having diploid number of chromosomes. Fertilization gives rise to the formation of seeds. The embryo is contained in the seed with the endosperm that served as food for the growing embryo. The embryo then grows by mitosis into a mature plant.  Squash flowers are unisexual which means that, male and female flowers grow separately in the same plant. You can easily distinguish the two by the presence of ovary at the base of the flower. This ovary contains the ovules (eggs) which when fertilized will develop into a fruit with the seeds inside.  Unisexual flowers need pollinators such as butterflies, bees or even wind that transfer the pollen into the pistil of the female flower and down the ovary.  Hence, for maximum squash production, pollination should be done by cutting the male flower and inserts it into the female flower  Papaya is a polygamous plant with three basic type of flowers: staminate (unisexual) – those bearing only male flowers pistillate (unisexual)- those bearing only female flowers hermaphrodites (bisexual)- those having both male and female reproductive organs in one flower. Gumamela is the best example of bisexual flower because both male and female reproductive organs are both found in the same flower  Corn is a monoecious plant, a hermaphrodite, where both the male and female reproductive parts are present in the same plant. Reproduction is carried out sexually. It is wind-pollinated. The tassel that springs up from the top of the plant after the leaves have appeared are the male parts of the corn plant. It comprises of branches which hold male flowers. These male flowers produce male sex cells which are contained in the pollen grains.  The ear is the female floral organ which evolves from the head of the shank. It is a tiny structure that emerges out of a leaf node usually situated above the ground and below the tassel. Pollination occurs when pollen grains fall on the silk (hair-like structures on each egg) when they are exposed.  Successively, male sex cells move down each silk to meet a single egg after which fertilization takes place. The egg, post-fertilization, matures into a kernel which holds an embryo and eventually emerges into a new corn plant.  However, the occurrence of silk and its exposure to pollen grains are very rare. Hence, to produce corn on a larger scale, the reproduction process of corn is carried out manually by fusing pollen grains with the silk of the corn. ARE YOU READY? Sexual Reproduction in Animals  Sexual reproduction in animals requires the fusion or union of a sperm and an egg in a process called, fertilization. Each egg and sperm share haploid number of chromosomes producing a new individual with diploid number of chromosomes. Thus, the new individual produced have unique characteristics which is the combined traits from both parents In animals, there are two major types of sexual reproduction – syngamy and conjugation.  Conjugation is a process of genetic recombination that occurs between two unicellular organisms by temporary fusion. This occurs in bacteria, protozoans, and single- celled fungi.  Syngamy is the most common type of sexual reproduction in multicellular sexual populations including humans. This involves the union of two haploid sex cells through the process of fertilization. There are two types of fertilization: internal and external.  Internal fertilization happens inside the female’s body by penetration of the male reproductive organ and deposit its sperm into the female. Most mammals use internal fertilization to reproduce such as cats, dogs, horses, cattle and including humans. External fertilization happens outside the female’s body. Fusion between male and female gametes happens in the outside environment. Sexual Reproduction by Conjugation Bacteria can reproduce asexually by binary fission and sexually by conjugation. A bacterium forms a conjugation tube called, pilus into another bacterium. Then, the two bacteria exchange genetic materials through the tube. This results in a bacterium with new combinations of DNA. After the exchange of genetic materials, the bacterium divides by binary fission resulting in new bacteria having new DNA in them. Sexual Reproduction by Syngamy Internal fertilization is common in many types of animals especially mammals. This involves insertion of the male reproductive organ into the female and deposit its sperm.  When seahorses mate, it is the female that inserts her ovipositor (a tube-like structure) in the male’s brood pouch. A pouch is a structure in the male’s body where the female deposits her eggs. When the eggs are contained in the pouch, the male then releases sperm into the pouch to fertilize the eggs. The male seahorse carries the fertilized eggs for about 2 to 4 weeks, depending on the species and give birth to between 100 and 1,000 babies and release them into the waters.  Earthworms are simultaneous hermaphrodite. Meaning, worms have both male and female reproductive organs. But they cannot join their two sex organs together in self- mating. Although, earthworms are hermaphrodite most need a mate to reproduce. During sexual intercourse, both sex organs are used by both worms by inverting each other so that sperms can be exchanged.  Fish and frogs reproduce by external fertilization. They deposit their eggs in waters while male fish or frogs ejects their sperm over the eggs and fusion takes place. The release of eggs into the waters is called, spawning. In some species, like salmons, they often travel long distances to a suitable location to deposit their eggs. ARE YOU READY? Asexual Reproduction in Plants and Animals Plants have two main types of asexual reproduction – vegetative and apomixis.  Vegetative reproduction results in new plant individuals without the production of seeds or spores. Many different types of roots exhibit vegetative reproduction such as ginger, potatoes, and the strawberry plant that uses stolons, which is also called a runner.  Apomixis results in the production of seeds without passing through the fundamental aspect of sexual reproduction. It is the development of seed or embryo without fertilization. The offspring produced is a clone of the female parent and are genetically identical.  Asexual reproduction in plants only requires a single parent for some plants to reproduce. Asexual Reproduction in Animals Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction comes from a single parent and inherit 100% of the genes of the single parent. There are different types of asexual reproduction in animals. These are: parthenogenesis, fragmentation, budding, regeneration, and fission.  Parthenogenesis is a natural form of asexual reproduction in which growth and development of an embryo occurs without fertilization. In animals, parthenogenesis means, development of an embryo from an unfertilized egg.  Fragmentation in multicellular organisms involves splitting of an organism into fragments. Each of these fragments develop into mature, fully grown individuals that are identical to their parents. Liver flukes are another parasitic worm that infects humans after eating infected undercooked meat and fresh water fish. As the name suggests, they travel from the intestine to the bile ducts and into the liver where they live and grow. Regeneration is a type of asexual reproduction in which the organisms is capable of re-growing certain body parts.  Budding is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. Bacteria, yeast, corals, flatworms, jelly fish, sea anemones, sea stars, sea urchins and other echinoderms are some animal species which reproduce through budding.  Fission is the division of a single entity into two or more parts and the regeneration of those parts to separate entities resembling the original. In this process, the organism duplicates its genetic material, and divides into parts with each new organism receiving one copy of DNA. Fission can be of two types – binary and multiple fission.  In binary fission, cell divides into two equal halves. Daughter cells are identical to each other and to their parent cell. Examples are: amoeba, euglena and other unicellular organisms. During multiple fission, organisms divide into numerous daughter cells. Examples to this are sporozoans and algae. Immune System of Plants and Animals Immune System  Immune System A network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens or disease- causing microorganisms. Immunity is defined as the body’s ability to protect itself from an infectious disease. Immunity is either innate or adaptive.  Innate immunity, also known as natural or genetic immunity. It is a type of immunity that an organism is born with. It is already encoded in the genes where it protects an organism throughout their entire life.  Natural or genetic immunity consists of: a) external defenses which work to protect an organism from pathogen exposure. b) internal defenses known as the second line of defense that address a pathogen once it has entered the body. Adaptive immunity also known as acquired immunity is defined as immunity that occurs following exposure to a pathogen. How the body defends itself against pathogens: 1. Pathogen Exposure 2. Antigen Detection 3. Immune Response Activation 4. Antibody Production 5. Pathogen Destruction 6. Memory Cell Formation This process is called adaptive immunity because the body "adapts" its response to specific pathogens. Remember: An antigen is a substance present in the pathogen that triggers an immune response. It includes chemicals, toxins, bacteria, viruses and other substances that come from outside the body. Even cancer cells have antigens in them that stimulates an immune response.  The antibody is antigen specific. Meaning, it is created by the immune cells to destroy a particular bacteria or virus. Adaptive immunity is further broken down into two subgroups: active and passive immunity. A passive immunity is a resistance to a disease or toxin where the resistance was gained without the immune system producing antibodies. It is already present from birth. Active immunity is further classified as natural and artificial. Active Immunity How it works: Your body produces its own antibodies in response to an antigen (a foreign substance like a virus or bacteria). Examples: Natural: Getting infected with a disease (e.g., chickenpox) and recovering. Your body produces antibodies to fight the infection and develops long-term immunity. Artificial: Vaccination. Vaccines introduce a weakened or inactive form of the pathogen, stimulating your immune system to produce antibodies without causing serious illness.  GREAT JOB! Thank your for your hard work!