HSC: Heredity Flashcards
SEXUAL REPRODUCTION
there is a mix of the parents’ genes. Each contributes their genetic material to the next generation.
ASEXUAL REPRODUCTION
offspring are genetically identical to each there and parent. Only one parent contributes their genetic material to the next generation.
EXTERNAL FERTILISATION
External fertilisation involves the fusion of gametes outside the body of a parent. It is most common in aquatic animals, where the water acts as a medium in which the gametes can travel. This method of fertilisation is susceptible to environmental influences, such as predators and pH changes. They usually release large quantities of gametes to compensate for losses.
INTERNAL FERTILISATION
Internal fertilisation involves the fusion of gametes inside the body of a parent. Terrestrial animals typically use internal fertilisation to avoid desiccation (drying out) of gametes or embryos. Internal fertilisation offers more protection to the gametes and embryos, but as a potential survival cost to the parent.
ADVANTAGES OF SEXUAL REPRODUCTION
Combination of chromosomes from two organisms increases variation, which assists with survival
DISADVANTAGES OF SEXUAL REPRODUCTION
Requires mating of two organisms which is dependent on syncing fertility cycles, and the production of offspring is lower and less prolific than asexual reproduction
Advantage of Sexual reproduction via internal
Increased likelihood of fertilisation as egg and sperm are in close proximity, with increased protection from the environment leading to higher survival rates of offspring. Less chance of desiccation of gametes
Advantage of Sexual reproduction via external
Large number of gametes produced generally means more off spring. It is also a simpler behavioural process which does not require mating rituals. More genetic variation
Disadvantage of Sexual reproduction via internal
Fewer offspring are produced, and it is more difficult to bring males and females into contact. There is higher risk of sexually transmitted infections passing between organisms
Disadvantage of Sexual reproduction via external
Species must produce larger numbers of gametes, which requires extra energy. It also requires a watery environment (may be difficult for amphibians )
Pollination
The transfer of male gametes (pollen) from the anthers (male) of one plant to the stigma (female) of the same or another flower so that fertilisation may occur (Stamen = male, Carpel = female)
Male reproductive part of plants
the filament and the anther (together called stamens). Anthers produce pollen which contains sperm cells of a plant.
Female reproductive part of plants
the female part (carpel) consists of the stigma, style, ovary and ovule.
Vegetative propagation
type of asexual reproduction in plants, it results in the parent producing a plant genetically identical.
Cuttings
the stem from the plant is cult and is planted in the soil that will gradually grows and turn into another plant. E.G., roses
Runners
Stems extending from the plant and along the soil. Runners will develop nodes which extend into the soil resulting in the formation of a new plant root allowing another to grow. E.G. strawberry
Bulbs
Bulbs are underground food stored organs that can grow and develop into new plants. E.G. onions
BUDDING
Budding in fungi such as yeast involves the parent cell developing a bud cells, a daughter nucleus. Overtime, this bus undergoes cell division (mitosis) while still being attached to the parent which may result in a chain of bud cells. The bus separates from its parent fungus when it grows to a sufficient size to be able to support itself independently. This now-separated bud undergoes further cell division to produce more bud cells. The result is genetically identical to the parent.
SPORES
Spores in moulds and mushrooms are micro reproductive units that can be formed as a result of mitosis or meiosis. Spores differ from gametes as they do not need to combine with another spore to form offspring. (spores are carried by the wind)
BACTERIA: BINARY FISSION
- A single cell divides into two identical daughter cells
- Begins with DNA replication where the genetic information of the bacteria is copied and divided in two.
- The cell elongates and splits into two (cytokinesis) producing daughter cells with identical genomic information (i.e. Clones of the parent).
- Very rapid
- Lack of genetic diversity in the resulting population lowers chance of organism survival
PROTISTS: BINARY FISSION, BUDDING
- For haploid protists, two haploid cells fuse to form a new cell, a zygote. Genetic material is combined oin a new fused nucleus. The zygote undergoes meiosis to form a new haploid cells.
- For diploid protists, adult cells undergo, meiosis to produce 4 gametes. Gametes fuse during fertilisation to form a diploid zygote, which will grow into a diploid adult.
hormones involved in the first trimester of pregnancy
high levels of progesterone also stimulate changes in the mother’s body. These changes include enlargement of the uterus, formation of a mucous plug to seal the cervix, growth of the maternal parts of the placenta, and breast growth.
hormones involved in the second trimester of pregnancy
high levels of oestrogen and progesterone are vital to continue maintaining pregnancy. However, the production of embryonic hcg declines and the corpus luteum deteriorates, stopping it from producing these hormones. Instead, the placenta takes over the role of producing oestrogen and progesterone.
