Biology Mod 5

Sexual Reproduction

Fusion of male and female gametes - sperm + egg

Making copies of likeness e.g. producing offspring that resembles parents. 

To survive genetic material must be passed on.

Sexual

Involves 2 parents

Mixing of genes

Offsprings are unique

Asexual

Involves only one parent

Offspring genetically identical (clones)

Haploid

Half the number of chromosomes

Gametes

Sex cell

Diploid

Contains full set of chromosomes 

Zygote

The first diploid cell formed when a sperm and egg fuse during fertilisation, containing a full set of chromosomes from both parents.

Internal Fertilisation

Union of gametes and development of offspring inside the female reproductive tract

External Fertilisation

Union of gametes and development outside of the body

Advantages of Sexual Reproduction

Genetic variation → enables a species to survive and reproduce in varied environment

Facilitates the selection of beneficial traits and elimination of unfavourable traits

Increasing beneficial genetic variation

Disadvantages of Sexual Reproduction

Energy must be used to produce gametes

Rely on environmental conditions and sometimes other species to ensure population

Finding a mate

Competing for males can be fatal

Parental investment is high shortening lifespan of parent

Internal Fertilisation Advantages

Less risk of genetic dehydration

Higher offspring survival

External Fertilisation Advantages

Typically in bodies of water

Mass releases of sperm + egg = high variation

Anther 

Pollen grains are formed

Stamen

Male parts of the flower

Fillament

Stalk that carries the Anther

Stigma

Sticky / where pollen adheres

Style

Joins the Stigma to Ovaries

Ovary

When ovaries are formed

Carpels

Females part of the flower

Ferns

Reproduce sexually by producing spores which germinate and produces sex cells

Seed Dispersal

Dispersal relies on the type of fruit in which the seeds occur, by animals, by wind and self dispersal

Pollenation

Pollen transferred from the anther (male) to stigma (female)

Fertilisation

Pollen (male gamete) is transferred to the Ovum (female gamete), Occurs inside the ovaries

Asexual Reproduction

Production identical offspring from one parent

Produces new individuals (offspring) by mitosis in which a daughter cell receives a copy of every chromosome of the parent cell

Advantages of Asexual Reproduction

Efficient and simple

Mitosis is less demanding

Works well when environment is relatively static

Less time + energy needed (no need to find a mate)

Disadvantages of Asexual Reproduction

All genetically the same

Rapid growth leads to overcrowding and increased competition for resources

Lack of genetic variation could cause death of entire population if conditions change.

Fission

Splitting of one cell into two (binary fission) or many (multiple fission) of equal size

Budding

Outgrowths from a parent call each smaller than the parent

Bacteria

Unicellular, microscopic prokaryotic that reproduce asexually

Quicker than eukaryotic cells (very quick)

Protist

Aquatic of most environments

Uni of multicellular

Autotrophic or heterotrophic (both asexually and sexually)

Membrane bound organelle

Fungi

Spores released e.g. from fruiting (mould, mushrooms and puffballs)

Budding e.g. Yeast

Chain of independent cells

Spores by meiosis (meiospores) are haploid reproductive cells

Structure sporangium

Asexual Plants

Lack of genetic variation

Rapid increase in number of plants growing in area

Advantages Sexual

High genetic variability

Facilitates adaptation

‘Speeds’ up evolution

Disdvantages Sexual

Energy cost

Courtship its time/resource consuming

Usually sacrifices the fitness of one sex to the other

Advantages Sexual

Saves energy

Courtship is an issue

Greatest increase in fitness for each individual

Disadvantages Sexual

How genetic variability

Adaptation to environment is difficult

“Retards” evolution

Divide (Cleavage stage)

1 zygote splits into 16

3 days mulgula → hollow sphere (blastocyst)

Implantation

Takes 5 days finished after 12 days

HGC doing work (hormones)

Placenta formed (umbilical chord)

Labour

Dilation - Child head is pushed (labour)

Expulsion stage - Baby pops out

Placental stage - Placenta is released

Menstrual Cycle

Balance of 4 different hormones - Lueinizing hormone (LH), Follicle stimulating hormone (FSH), Oestrogen, Progesterone

Avg cycle = 28 days

Menstruation (1 - 4 days)

Uterine bleeding, accompanied by shedding of the endometrium

Pre - Ovulation (5 - 12 days)

Endometrial repair beings, development of ovarian follicle, uterine lining gradually thickens

Ovulation (13 -15 days)

Rupture of mature follicle, maturing egg

Secretion (16 - 20 days)

Secretion of watery mucus by glands of endometrium, cervix and uterine tubes, movement and breakdown of unfertilised egg, development of corpus lutuem.

Pre - Menstruation (21 - 28 days)

Degeneration of corpus lutuem, deuterium of endometrium

Fertilisation

Fusion of two haploid gametes to form a single diploid zygote cell

Conception

Occurs when haploid nucleus of the egg fuses with that of the sperm forming, a diploid fertilised cell called a zygote 

Following fertilisation the egg divides as it travels along the oviduct and begins developing into and embryo