Mod 5: Reproduction

Question 1

What is reproduction?

Answer 1

Reproduction involves one or more parents producing one more offsprings. It is a fundamental evolutionary process that ensures the continuity of species. Without reproduction species numbers wouldn’t increase, thus no further life on earth, which again reiterates no evolution

Question 2

What is asexual reproduction and what species are involved?

Answer 2

Asexual reproduction is a type of reproduction where only one parent produces the offspring which its genetically identical to the parent. Gametes (sex cells ) cells are not involved. Bacteria, yeast (fungi), hydra (protist), and some plants (mosses and fern) asexually reproduce

Question 3

What is sexual reproduction and what species are involved?

Answer 3

Sexual reproduction is a type of reproduction where 2 parents are involved for the production of an offspring. Gametes ( egg and sperm) are involved and the offspring produced is genetically different from the parents. Most animals such as crocodiles, kangaroos, turtles sexually reproduce as well as placental mammals such as humans

Question 4

What are the advantages and disadvantages of asexual reproduction

Answer 4

Advantages: Less time consuming, hence energy efficient as there is no need to find a mate as the one parental organism has the ability to reproduce on its own. Another advantage is that the population can increase rapidly in favourable conditions such as the rapid growth of rhizopus (enoki mushroom) on bread in moist conditions.

Disadvantages: The offsprings are genetically identical to the population, thus no or limited genetic variation in the population. All the species sharing the same weaknesses and certain characteristics. This can be disadvantageous as if a selection pressure appeared the population could be wiped out at once.

Question 5

What are the advantages and disadvantages of sexual reproduction?

Answer 5

Advantages: There is great variation in the offspring. This is advantageous as they are able to live in different environmental conditions, as well as survive if there was change in the environment, hence ensuring its continuity

Disadvantages: Producing the offspring is time consuming as it involves finding mate, courtship behaviour and giving birth. Both the parents put in the a huge amount of energy in the process as well as after birth, them needing to take of the newborn.

Question 6

Explain the process of internal fertilisation

Answer 6

Internal fertilisation is a type of sexual reproduction as there is a fusion of gametes and organisms living on land carry out the process for production of their offsprings such as birds, mammals and reptiles. It occurs when the male animal transfers its gametes into the females body through a tube in the penis known as a process called copulation. Once the gametes arrive there is fusion with the eggs, in which fertilisation has taken place, forming a zygote.

Question 7

Why do land animals carry out internal fertilisation?

Answer 7

Internal fertilisation involves fertilisation (fusion of gametes) inside the body. Land animals carry out this type of reproduction so their gametes don’t dehydrate. As the mother has a moist reproductive tract, the gametes don’t dehydrate, hence successful fertilisation taking place. If the gametes were to be fertilised externally on dry land, they would be exposed to humidity and wind, affecting the gametes negatively, thus no fertilisation taking place as gametes need a watery environment so there can be fusion.

Question 8

What is one advantage and disadvantage of internal fertilisation?

Answer 8

Internal fertilisation involves the fusion of gametes (fertilisation) inside one of the parental organisms body.

The chance of fertilisation is really high as the male gametes are released in a confined space, which means a higher chance of successfully fusing with the female gamete (egg)

Another advantage is that only a few offsprings need to be produced as the chance of them perishing is really low due to the zygote being protected from predators and so being able to grow safely in the mothers womb.

A disadvantage is that it requires more effort and energy in the process as well as being time consuming due to even needing to care for the offspring after its birth

Question 9

What are the types of asexual reproduction?

Answer 9

Binary fission, spore formation, budding, vegetative propagation

Question 10

How does hydra reproduce?

Answer 10

Hydra, polyp like organisms with a tubular body, reproduces asexually through the process of budding

Question 11

Explain the process of external fertilisation!

Answer 11

External fertilisation involves the fusion of the gametes (sperm and eggs) externally, mostly occurring with organisms that live in water environments such as spawning amphibians and bony fish. The female species releases a large amount of its gametes in the water, that being eggs and at the same time the male species releases a large amount its gametes (sperm) in the water. The eggs are then fertilised externally by the sperm forming zygotes. Large amounts are released to ensure fertilisation of some of the gametes as some are prone to predators and currents of the water, resulting in their death.

Question 12

Why do aquatic animals carry out external fertilisation?

Answer 12

Aquatic animals carry out external fertilisation, that is fusion off the gametes in the water so the successful fertilisation of the gametes can take place, to form a zygote. In the water the gametes are hydrated ensuring fertilisation

Question 13

What are the advantages of external fertilisation?

Answer 13

In external fertilisation, the mother will expend less energy on gestation as all the processes, that is the development stage will occur outside the body. Another advantage is that it is less time consuming due to the eggs being produced continuously at a constant rate and at a greater amount making the process of reproduction much faster

Question 14

What is the disadvantage of external fertilisation?

Answer 14

One disadvantage is that the fertilised zygotes are vulnerable to environmental elements such as predators, temperature and infection. This explains why water organisms such as frogs and fish release large amount of gametes. Its because some of them will perish leaving a limited population

Question 15

Explain the process of cross pollination and outline one advantage and disadvantage of the process

Answer 15

Flowering plants sexually reproduce through the process of cross pollination. It involves taking the pollen from one plant by a carrier commonly bees which is then placed on the stigma of another plant. The pollen then travels down the style independently and into the ovary in which fusion of the male gametes and eggs found in the ovules take place forming a seed. The matured seed is then dispersed by external agents such as wind.

One disadvantage is that the flowering plants need to develop structures to attract pollinators so there can be transfer of pollen, requiring energy

An advantage is that it ensures and great genetic variation in the offspring as genes from 2 parents (2 plants) is transferred to the offspring.

Question 16

How do plants asexually reproduce?

Answer 16

Some flowering plants have the ability to reproduce asexually known as self pollination. In this process the plant will self pollinate itself and this is done by lowering the stamen until it reaches the stigma so fusion of the male and female gametes can take place, resulting into a seed.

Another method in which plants can reproduce asexually is vegetative propagation. Vegetative propagation is defined as the production of new identical plants through vegetative structures such as roots, stems and flowers.

Question 17

Identify the female and males gametes in a flowering plant

Answer 17

The male gametes are found in the pollen (anther), that is part of the stamen and the female gametes (ovules) are located in the ovary of the stigma, a part of the carpal .

Question 18

In what organisms does binary fission occur in?

Answer 18

Protists (unicellular eukaryote) and bacteria (prokaryote). Examples of bacteria include cyanobacteria and protists include amoeba, euglena,

Question 19

How is binary fission different in both unicellular eukaryotes and prokaryotes (not too important!)

Answer 19

Binary fission is defined as the splitting of one singular parental cell into two identical offsprings (cells). This process occurs in protists (amoeba and euglena) and bacteria (cyanobacteria). Although the process is the same (dividing of one parent cell), in both unicellular eukaryotes and prokaryotes, there are some differences. In amoeba, the division is referred to as multiple fission, which means the nucleus will divide multiple times before cytokinesis ends the cycle whereas in prokaryotes.

Question 20

What are the genetic consequences of asexual methods of reproduction?

Answer 20

In asexual methods of production, the offsprings produced will have no or limited genetic variation, which can be disadvantageous, as the offsprings sharing the same weaknesses and certain characteristics, they would have difficulty surviving changes in environmental conditions, eventually being wiped out of the population.

Question 21

What is the birth mark left on budding on the daughter yeast cell?

Answer 21

Birth scar… bud scar (mark on parent cell)

Question 22

What is cytokinesis?

Answer 22

Cytokinesis ends most cell division cycles such as mitosis and meiosis. It it is the complete separation of the cytoplasm, resulting into two or more new cells.

Question 23

Outline why offsprings produced through asexual reproduction have little genetic variation.

Answer 23

In some cases, offspring produced through asexual reproduction have, little variation and this is due to mutations that take place when the DNA is replicated. Where as in other cases if there are no mutations, then the same genetic information will pass down to to the offsprings resulting in them having the no variation, as the genetic information is the same as the parent

Question 24

Identify the name of a part in a flowering plant (angiosperm) that consists of male reproductive organs. Identify the organs

Answer 24

Stamen and includes the anther (pollen, consisting of male gametes) and filament

Question 25

Identify the name of the part in a flowering plant that consists of the female reproductive organs. Identify the organs

Answer 25

Carpel or pistil and includes the stigma, style and ovary (consists of ovules)

Question 26

What is the function of the ovary in a flowering plant and where it is located?

Answer 26

The ovary is located at the bottom of the carpel and it produces and stores ovules so fertilisation can take place once the pollen arrives.

Question 27

What is the function of the stigma and where is it located?

Answer 27

The stigma is the top part of the carpel and its sticky so once the pollen arrives it can get stuck onto it. This allows for the pollen tube to be produced down the style so that the pollen has a way to get to the ovary and fertilise the eggs

Question 28

Why is fertilisation an important part of sexual reproduction?

Answer 28

Fertilisation occurs in sexually reproducing plants, placental mammals such as humans and many other animal species. Fertilisation is said to have occurred, when there is fusion of the haploid male and female gamete, resulting into zygote containing the diploid number of chromosomes, hence the original number of chromosomes being restored. This is an essential part of sexual reproduction as the offspring needs to contain the full amount of genetic information, so it is able to continue its life and survive in the external environment when it released from the mother’s womb, thus ensuring its continuity.

Question 29

Why is a species that reproduces sexually more likely to survive a sudden change in environment than a species which reproduces asexually?

Answer 29

In sexual reproduction the offspring/s formed have a source of genetic variation/variability due to the process of meiosis to form the genetically different gametes and the formation of zygote, increasing genetic variation in the offspring. This variation ensures them protection from changing environmental conditions, whether it be favourable or unfavourable hence contributing to their long-life expectancy (continuity). In asexual reproduction the offspring’s produced have no source of genetic variation which means they would share all the same weaknesses, so if unfavourable environmental conditions came by, they would all wipe out from the population

Question 30

What is a zygote?

Answer 30

A zygote is a fertilised egg that results from the fusion of the male gamete (sperm) and the female gamete (egg)

Question 31

What is a gamete

Answer 31

A gamete is a reproductive sex cell that is produced in the gonads of both the male and females body. The female sex cell is referred to as an egg and is produced in the ovaries however the male gamete is referred to as a sperm and is produced in the testes