Introduction to Reproduction

Introduction to Reproduction

• Asexual reproduction doesn't require gametes or sex cells
• Sexual reproduction requires gametes

Types of Asexual Reproduction

• Fission involves the division of a body into two or more equal parts, Paramecium exhibits this
• Fragmentation is when the body breaks into parts, each capable of becoming a complete individual. Animals use regeneration to replace missing parts
• Spirogyra, Oedogonium, and detached starfish use fragmentation
• Budding involves a new individual arising as an outgrowth, or bud, from its parent. Hydra is an example
• Sporulation occurs when a new individual forms from an aggregation of cells surrounded by a resistant capsule or spore. Fungi, like Rhizopus, exemplify this

Types of Gamete Union

• Isogamy involves the fusion of similar gametes, usually motile. Chlamydomonas and Spirogyra demonstrate isogamy
• Heterogamy is the fusion of dissimilar gametes. Oogamy, where a large immotile egg is fertilized by a small motile sperm, is a type of heterogamy

Terms for Sexual Reproduction

• Bisexual reproduction involves the union of gametes from two genetically different parents, like in humans and papayas
• A hermaphrodite has both male and female reproductive tissues. Internal self-fertilization is rare in animals. Worms need to receive sperm from another male to fertilize their oocytes. Barnacles and worms are examples

Comparing Asexual and Sexual Reproduction

• Asexual reproduction involves one parent, while sexual reproduction involves two
• Asexual reproduction doesn't require gamete union, but sexual reproduction does
• Asexual offspring are genetically identical to the parent (clones), while sexual offspring are hybrids of both parents

Stages of Animal Development

• Development involves the formation of sex cells, zygotes, and subsequent life stages, terminating in death
• Gametogenesis is the stage of development that produces haploid gametes
• Haploid (n) condition means a cell has half the normal chromosome number
• Diploid (2n) means a cell has the full chromosome number

Stages of Animal Development (cont.)

• Fertilization results in a unicellular diploid zygote
• Cleavage involves a series of mitotic divisions to produce a multicellular blastula from a unicellular zygote
• A totipotent cell can differentiate to become any kind of cell
• Gastrulation involves morphogenetic movements to produce a gastrula with distinct germ cell layers
• In vertebrates, gastrulation results in three layers: ectoderm, endoderm, and mesoderm

Germ Layers and Their Fates in Vertebrates

• Ectoderm becomes the nervous system (brain & spinal cord), epidermis, and sense organs
• Mesoderm develops into muscles, bones, cartilage, and circulatory, excretory, and reproductive organs
• Endoderm forms digestive and respiratory organs, endocrine glands, germ cells, and gametes

Organogenesis and Growth

• Organogenesis is the stage where germ layers differentiate into specific organ systems
• Growth is characterized by an increase in size

Types of Twins

• Monozygotic twins, or identical twins, result from the union of sperm and egg that forms a single zygote that splits during the first cleavage stage
• Dizygotic twins, or fraternal twins, result from two or more separate fertilization events where the resulting zygotes develop simultaneously

Male Reproductive System

• Testis produces sperms
• Epididymis is for sperm storage
• Scrotal sac/scrotum supports the testis and epididymis
• Vas deferens carries sperm from the testis before joining the urethra
• Urethra connects to the bladder and is a passageway for both sperm and urine, terminating in the penis
• Seminal vesicle secretes fluid with fructose that gives semen its alkaline properties to protect sperm
• Prostate gland secretes fluid that provides alkalinity, proteolytic enzymes, citric acid, phosphatases, and lipids for semen
• Bulbourethral glands produce pre-ejaculate to lubricate the urethra; in addition to neutralizing traces of urine

Female Reproductive System

• The clitoris is the equivalent of the penis in females
• The vagina is the main entrance to the female reproductive tract
• The cervix is where the vagina ends, projecting into the uterus
• The uterus is where the embryo develops, with thick muscular walls, blood vessels, and an endometrial lining

Uterus and Pregnancy

• The endometrial lining/endometrium is the innermost lining where the embryo implants and develops
• Fallopian tubes, or oviducts, connect the uterus and ovaries, and this is where fertilization takes place
• Ovaries release oocytes during ovulation and are collected by the fimbriae of the fallopian tubes

Human Development Stages

• Fertilization occurs in the fallopian tube, resulting in a unicellular zygote
• Cleavage also occurs in the fallopian tube
• The morula is a solid ball of cells, while the blastocyst consists of an inner cell mass and the trophectoderm, from which the placenta develops
• Implantation is when the blastocyst implants in the endometrium and signals the start of pregnancy
• Gestation lasts up to nine months
• The human embryo corresponds to the first two months
• The human fetus corresponds to months 3-9.

The Menstrual Cycle: Ovarian Cycle

• Follicular phase is when follicles begin to mature. It's marked by FSH and LH secretions stimulating oocyte maturation and estrogen stimulates uterine lining growth
• Luteal phase is the part after oocytes are released from follicles, where the remains become the corpus luteum and secrete progesterone to stimulate the uterus for gestation

The Menstrual Cycle: Uterine Cycle

• Menstrual phase, also known as the "period," corresponds to the early follicular phase of the ovaries and involves the endometrium sloughing off
• Proliferative phase corresponds to the latter follicular phase and is when the endometrium heals and thickens due to estrogen secretion
• Secretory phase corresponds to the luteal phase and is when the endometrium undergoes final changes by receiving the embryo.

Contraception

• Ovulation-suppressing methods prevent the oocyte from maturing
• Barrier methods prevent fertilization with condoms, diaphragms and cervical caps
• Chemical methods use spermicidal jelly or foam to kill sperm on contact
• Surgical methods prevent fertilization through surgery, like vasectomies or tubal ligations
• Implantation-suppressing methods prevent the blastocyst from implanting in the endometrium with IUDs
• Morning-after pills prevent the action of hormones that prepare the uterus

Other Contraceptive Methods

• Abortion removes the embryo/fetus
• Coitus interruptus requires the man to remove the penis before ejaculation
• Abstinence is when a man and woman do not engage in sexual intercourse

Plant Life Cycles: Generalities

• In the general plant life cycle, the mature, multicellular organism is a diploid sporophyte
• Some cells undergo meiosis to produce haploid gametes
• Released gametes fuse to form a zygote
• The zygote develops by mitosis into a sporophyte

Plant Life Cycles: Gametophytes

• In some plants, the dominant part is a multicellular, haploid gametophyte
• The haploid cell number is produced by mitosis and mitosis can releases individual cells that may act like gametes
• • A gametophyte* is a haploid stage which can produce gametes and these gametes fuse

Plant Life Cycles: Sporophytes

• For plants which are diploid, that is termed a sporophyte
• A Sporophyte produces haploid spores by meiosis in structures called sporangia

Types of Plant Life Cycles: Haplontic

• A haplontic life cycle involves haploid stages that are multicellular
• The only diploid stage is a fertilized egg cell
• For example, green algae such as Chara is multicellular with gametes that fuse, creating a zygotes

Types of Plant Life Cycles: Haplodiplontic

• The Haplodiplontic life cycle covers diploid and haploid generations
• Mosses have a multicellular haploid stage which produces gametes
• Gametes fuse to produce a zygote, undergoing mitosis to produce a multicellular sporophyte
• Sporophytes undergo meiosis to produces meiospores

Types of Plant Life Cycles: Diplontic

• A diplontic life cycle has diploid stages that area multicellular, with haploid cells that are represented by the gametes
• Found in flowering plants and most animals
• All cells are diploid except for mature haploid sex cells, the gametes

Flowers

• Angiosperms are flowering plants, which are plants that produce reproductive structures
• Flowers are reproductive structures in flowering plants

The Flower: Whorls

• There are four main whorls
• Sepals are the outermost whorls of a flower
• Petals are found in the whorl inner to the petal, brightly colored and collectively called the corolla
• The stamen is the whorl inner to the petals

Stamen

• The stamen is the male reproductive structure
• it Bears the male sporangia, also known as microsporangia
• The anther is the part that contains microsporangia that develops into pollen grains
• The filament serves as the stalk of the anther

Carpels

• Carpels are innermost whorls of the flower
• The carpels are the female reproductive structure
• it Bears the female sporangia, also known an megasporangia
• The stigma part attaches during pollination
• The style serves as the stalk to the stigma, leading to the ovary

The Ovary

• The ovary is the base of the carpel, contains one or more ovules, and eventually becomes the fruit
• The ovule contains the female sporangia and becomes the seed

Types of Flowers: Whorls

• In complete flowers the following need to be present, sepals, petals, stamen and carpels
• Incomplete flowers lack one or more of the floral whorls

Types of Flowers: Reproductive Whorls

• Perfect/ bisexual Flowers have both stamens and carpels
• Imperfect/Unisexual have either stamens or carpels

Types of Plants: Flowers

• Monoecious plants contain perfect, both staminate and carpellate flowers
• Dioecious plants have only the staminate or carpellate flower

Plant Types: Monoecious and Dioecious Development

• Gametophyte goes through gametogenesis
• The microsporangium in the anther contains microsporocytes
• Microsporocytes undergo meiosis, producing haploid microspores which develop into a pollen grain

Female Gametophytes

• They develop through gametogenesis which contains megasporocytes
• One megasporocyte will undergo meiosis
• This will produce four haploid megaspores

Megaspores

• Three megaspores degenerate
• Remaining megaspore divides mitotically 3 times
• an embryo sac with eight haploid nuclei forms, partitions membrane to become multicellular

Pollination

• Pollination is the placement of pollen from the anther to the stigma
• Requires transfer of pollen grain from the anther to the stigma
• The pollen grain is the immature male gametophyte, derived from microsporocytes inside the microsporangia

Pollen Grains

• Inside the pollen grain there are tube cells and generative cells
• The tube cell will develop into the pollen tube
• the generative cell divides into two sperm nuclei
• pollen travels via animal or wind

Double Fertilization

• Inside a pollen grain
• there is an egg cell and generative cell to produce 2 sperm
• the tube cell becomes the pollen tube
• there will be single union with one sperm, creating a zygote for the endosperm

Structures

• The embryo sac is female gametophyte found inside the ovule and derived from the megasporocyte
• The micropyle is the opening of the ovule, surrounded by the embryo sac

Embryo Development

• The zygote divides mitotically
• It produces the proembryo and suspensor
• The Proembryo receives nutrients
• Cotyledons appear on the proembryo

Maturation

• The Ovary nature into a fruit while the ovule becomes the seed
• Seeds may become dormant for some time

Seed Germination

• This is the transformation from sees to seedling
• Seed undergoes imbibition to break dormancy
• Primary meristem develop the radicle and plumule

Germination Types

• epigeal types occur above ground, thus exposing plumule and hypocotyl
• hypogeal types occur underground, thus concealing the hypocotyl
• Primary meristems differentiate and then become tissue of plants

Nutrients

• Nutrients are required for growth and maintenance
• Autotrophs create their own food
• Heterotrophs need to consume food
• Water and oxygen are nutritional needs of plants

Nutrients: Key Factors

• Essential nutrients are required at various levels
• Macronutrients are needed at the level of >0.5% of dry weight
• Micronutrients are required in trace amounts

Absorption Routes

• Symplast routes go though the plasmodesmata
• apoplast routes go via cell walls
• Both routes described how water needs to get to tissues within plants

Absorption Structures

• Root hairs increase surface level
• Root nodules exist where bacteria aid plants with nitrogen fixation

Mycorrhizae

• This refers to the symbiosis of young roots and fungi
• The fungus gains sugars and nitrogen
• The plant absorbs minerals better

Symbiosis

• Symbiosis is plants and soil microbes
• Symbiosis of plants and fungi is also used
• Parasitism is a relationship where one benefits to the detriment of the other
• Predation is the act of killing for food

Calories in Food

• A calorie is a unit of energy
• Calories raise the temperature of water, thus allowing energy to be contained in food

Animals

• Carbohydrates are the major energy source
• On average they are 4 calories per gram

Energy

• Proteins can be used as energy
• Lipids build structures
• Lipids are 9 calories a gram

Essential Nutrients

• These are only attainable in foods eaten
• Essential amino acids helps synthesize proteins
• Essential fatty acids can be sued for special lipids
• Vitamins are organic with normal metabolism
• Trace elements can build tissues

Food Uptake: Endocytosis

• Phagocytosis can engulf particles
• Pinocytosis uptakes fluid
• Receptor mediated intake is via receptor coated pits

Feeding Mechanisms

• Substrate feeders live on their food source
• Filter feeders water and capture organisms Fluid feeders get nutrients from hosts
• Bulk Feeders eat large food, like snakes

Digestion Types

Food vacuoles fuse with lysosomes

• Gastrovascular occurs via a single opening
• Complete digestion is essentially a tube

Food Processing

• The liver secretes bile
• The gallbladder stores bile
• Pancreas produces enzymes, buffers, and insulin

Food Processing: Main Stages

• Ingestion is eating
• Digestion breaks food to energy Absorption goes from tube to fluids
• Elimination is rejection from the tube

Steps: Organs

• Oral cavity is initially chewed
• Pharynx and Esophagus connect oral cavity
• Stomach then regulates small intestine

Other Key Facts

• Gastric juice is made of hydrochloric acid
• Food turns to a liquid called chyme

The Small Intestine

• Very long (6 meters)
• Composed of duodenum, jejunum, and ileum
• Most macromolecule breakdown happens in the duodenum
• Absorption happened in the ileum, surface increases with villi

Key Organs cont.

• Pancreas, liver and gall bladder are digestive organs
• Large intestines focus and absorb, and have bacteria
• Absorbs salts

Actions & Steps

• The rectum is the extension of the large intestine
• The Anus is where feces is expelled

Food Processing

• Carbohydrate breakdown is done in the mouth
• The small intestine absorbs resulting sugars
• Small intestines produce free amino acids
• Fat breakdown happens in the small intestines
• Epithelial cells release fat

Final points

• Vitamins are passive transport, or active Substances are through osmosis and diffusion
• Nutrients proceed from liver
• Tissues of bodies spread depending on conditions"