Module 5: Heredity Flashcards
What is sexual reproduction?
the process of forming a new organism from the fusion of the offspring’s parents male and female gametes. They are not geneticall identical.
What does sexual reproduction require?
-what happens
Requires (meiosis) for the production of gametes- to form a zygote with a full complement of chromosomes. Each gamete is haploid. The cells of the zygote divide (mitosis) and the embryo continue to grow.
What is asexual reproduction?
The process of forming an offspring from just one parent through cell division. There is no fusion of gametes. They are genetically identical.
What is reproductive success?
The ability to reproduce of an individual
What is the gene pool?
The genetic material of all organisms in a population
What is the biological fitness?
The likelihood of genes appearing in the next generation
Important for continuation of a species
What is internal fertilisation?
The fusion of gametes inside of the body of a parent
What animals use internal fertilisation?
Terrestrial animal typically use this to prevent exposure and desiccation of gametes or embryos
what are the benefits of internal fertilisation?
Offers more protection to gametes and embryos but puts parent at survival risk
More selective of their mate
Less chance of desiccation
What is external fertilisation?
The fusion of gametes outside of the body of a parent
What animals use external fertilisation?
Aquatic animal use the water as a medium for the gametes to travel
What are the pros and cons for external fertilisation?
It is susceptible to environmental influences e.g. predators and PH changes
Use of spawning to release large quantities of gametes to compensate for losses ( requires a short burst of high energy)
Easier way to find mates
More genetic variation
Do flowers reproduce asexually or sexually?
both
ROLE OF
Flowers
petal
nectar
flowers are the reproductive organs of sexually producing plants; the petals and nectar are used to lure animals and to assist with delivery of pollen.
Sexual reproduction in plants
Offspring are produced by the fusion of two haploid gametes. Male gametes (pollen) are produced and transferred to the female ovules. Pollination is assisted by wind or insects. After pollination, fertilisation ( after pollen lands on stigma, a pollen tube grows down through the style into the ovary. It is then moved down to try to fertilise the ovules) occurs and the ovules grow into seeds in a fruit, which disperses once ripe. The seed is then freed from the fruit.
Plants pollination sexual
Male gametes (pollen) are produced and transferred to the female ovules. Pollination is assisted by wind or insects. after pollen lands on stigma, a pollen tube grows down through the style into the ovary. It is then moved down to try to fertilise the ovules
Where do seeds grow in plants?
the ovules grow into seeds in a fruit, which disperses once ripe. The seed is then freed from the fruit.
What are the male parts of a plant?
Stamens are made up of:
The filament- supports the anther
Anther- pollen produced here
What are the female parts of a plant?
Carpel is made up of the
Stigma: pollen grains reach the stigma (pollination)
Style: pollen tube grows down through the style into the ovary
Ovary: where eggs cells are
Advantages and disadvantages of sexual reproduction in plants?
Advantages: Creates a genetic diversity within a species, leading to higher levels of disease resistance and a greater ability to adapt to changing conditions.
Disadvantages: Can prevent favourable genes from being passed to offspring
What is asexual reproduction in plants?
Structural modifications to the stem or roots of the plant results in the production of new individuals, without the need for production of seeds or spores
What is vegetative propagation? Provide examples
It results in the parent producing a plant that is genetically identical. E.g. cuttings, runners and bulbs
Cuttings in plants:
Cuttings: the stem from the plant is cut and planted into soil, eventually grows into another plant
What is totipotency?
Totipotency- each cell has the ability to do the job of every other cell
Runners in plants:
Runners: Stems extending from the plant along the soil, nodes develop along it which extend into the soil and form a new plant root. Here another plant can grow while being connected to the parent plant
Bulbs in plants:
Bulbs: Underground food storage organs. When a new plant forms the bulb provides nutrients for the plants survival
advantages of asexual reproduction in plants
Advantages: Offsprings are clones of parent plants, meaning the favourable traits are effectively passed through generations. This is economically advantageous for farmers to ensure consistency in their crops. It is less energy-intensive, meaning the population can increase rapidly and exploit suitable habitats quickly
Disadvantages of asexual reproduction in plants
Disadvantages: Pathogens may spread easily from parent to offspring, resulting in less genetic diversity. This increases the susceptibility of species to new diseases, and evolution is reduced due to lack of genetic variation.
How do funghi sexually reproduce?
Plasmogamy: two genetically different cells fuse together
Karyogamy: the nuclei fuse
Meiosis: gametes are generated which produce spores that are distributed into the environment
Fungi asexual reproduction: fragmentation
Fragmentation: pieces of hyphae can separate and become new colonies
List the ways in which fungi can asexually produce
fragmentation, budding and spores
Fungi asexual reproduction: Budding
the nucleus divides and a bulge forms in the side of the cell which is then split off by cytokinesis, and the bud detached itself from the mother cell when it is of a sufficient size. This separated cell can support itself independently and undergoes further cell division to produce more bud cells.
Fungi asexual reproduction: SPores
mitosis or mitosis produces genetically identical cells to the parent, which are distributed into the environment by wind or vectors . Spores differ from gametes as they do not need to combine with another spore to form offspring. Hyphae (fine thread like structures) branch out and have ends that are capable of producing sporangia.
Sexual spores may be developed when opposite gender hyphae combine to develop a zygospore, The zygospore is diploid and each hypha are haploid. The zygospore undergoes meiosis to produce haploid spores which are dispersed into the environment. The process repeats and results in genetically different hyphae.
Advantages and disadvantages reproduction in fungi
advantages:
Production of spores allows for offspring to be widely distributed, increasing colonisation
They can be produced in large numbers
Combination of sexual and asexual methods means fungi have a choice
Asexual is fast and not energy-intensive
Sexual increases genetic variability
Disadvantages:
Asexual reproduction may result in offspring which are only suited to one habitat
How do bacteria reproduce?
Binary fission
Binary fission in bacteria:
A single cell divides into two identical daughter cells
Begins with DNA replication where it is copied and divided into two
The cell elongates and splits in two (cytokinesis), producing daughter cell clones
Binary fission in bacteria: advantages
Very rapid and only requires a single organism in order to produce offspring
Binary fission in bacteria: disadvantages
Lack of genetic diversity, lower chance of organism survival. Thus can be overcome by high rates of mutation during DNA replication and HGT which can be passed from bacteria to bacteria
Sexual reproduction in protists
For haploid protists, two haploid cells fuse to form a zygote. Genetic material is combined in a new, fused nucleus. The zygote undergoes meiosis to form new haploid cells
For diploid protists, adult cells undergo meiosis to produce 4 gametes. Gametes fuse during fertilisation to form a diploid zygote.
Asexual reproduction in protists
Binary fission is the most predominant method
Budding occurs when a new organism grows from the body of the parent organism to form a new colony
Protists reproduction: Advantages + Disadvantages
Advantages:
If they reproduce sexually they have an evolutionary advantage over asexually producing protists.
Allows for greater variation
Disadvantages:
Asexual reproduction can often be disadvantageous to host organisms during pathogenesis. Fast reproduction at little energy cost to the protist makes them more effective as disease-causing agents
Define fertilisation:
Fertilisation: Gametes meeting and combining to form a zygote
What is Gametogenesis?
Gametogenesis is the name of the gamete formation process and can be divided into spermatogenesis (producing sperm) and oogenesis (formation of mature egg cells).
What is spermatogenesis?
producing sperm
What is oogenesis?
formation of mature egg cells
What hormone is produced in the testes?
-what is its role
The hormone testosterone is produced in the testes and plays a role in producing sperm cells.
Fertilisation in humans:
The fertilisation occurs in one of the fallopian tubes of the female’s body. The sperm enters the vagina, travels up through the uterus and then along one of the fallopian tubes where it can combine and fertilise the mature egg.
How does a zygote form? Humans
The gametes fuse to form a zygote, a single cell with 46 chromosomes (23 from each parent).
How does a blastocyst form?
During fusion, the head of the sperm cell detaches from its tail (flagellum) and activates the egg resulting in cell division. The resulting product is called a blastocyst.
What is implantation? humans
The process whereby the blastocyst adheres to the walls of the uterus.
Why is implantation important?
This establishes the blastocysts access to nutrients, allowing it to develop into an embryo ( blood vessels surrounding the blastocyst carry blood which has dissolved nutrients).
What happens if the blastocyst implants successfully in the uterus?
If the blastocyst implants successfully in the uterus, the cells continue dividing, moving to form two distinct structures.
Implantation:
-inner cell mass
Three or four blastocyst cells develop into the inner cell mass, which over the next few weeks will form into the recognisable structures of a human embryo, with a head, beating heart and tiny limbs. Some of these cells also develop into a foetal membranes that form a fluid-filled protective ‘bag’ around the embryo.
Implantation
-trophoblast
The remaining 100 or so blastocyst cells form a structure called the trophoblast, which will provide the baby’s contribution to the placenta.
How is HCG produced?
It is produced by the placenta after implantation.
WHy is HCG important?
It is mainly responsible for the early pregnancy symptoms ranging from missed menstruation to nausea, vomiting and fatigue.. It supports the function of the corpus luteum, a temporary structure in the ovaries essential in early pregnancy. It’s the hormone detected by pregnancy results.
Outline HCG trends throughout pregnancy:
Increases drastically in the first 10 weeks and slowly declines throughout the pregnancy
What does progesterone do?
It maintains the functionality of placenta and prevents sudden movement and contraction of the uterus. It stimulates growth of blood vessels that supply the womb and inhibits contraction of the uterus so it grows as the baby does. It also strengthens pelvic wall muscles for labour.
Outline progesterone trends throughout pregnancy:
Progesterone levels rise after the first trimester
What is oesterogen?
It is an ovarian hormone that is controlled by luteinising hormone (LH) that triggers ovulation.
What is oestrogens role during pregnancy?
An important role of estrogen is to facilitate the maturing of lungs, kidneys, adrenal gland, liver and bone It helps the uterus grow, maintains its lining, activates and regulates production of other hormones.
Outline oestrogen trends throughout pregnancy;
oestrogen levels increase steadily during pregnancy and reach their peak in the third trimester. The rapid increase in estrogen levels during the first trimester may cause some of the nausea associated with pregnancy.
What is the role of oxytocin?
Facilitates the delivery process by helping in the control of the uterus and also stimulates the mammary glands to produce milk.The hypothalamus in the brain produces oxytocin and stores it in the pituitary gland (situated below the hypothalamus). Upon stimulation of hypothalamus neuron cells, the pituitary gland will secrete oxytocin into the blood.
Oxytocin levels at labour + effect
Oxytocin levels rise at the start of labour stimulating contractions of uterine muscles. It triggers production of prostaglandins, which increase contractions further.
