1.Excavates, diplomonads and parabasalids, lacking mitochondria were classified

ID: 59098 • Letter: 1

Question

1.Excavates, diplomonads and parabasalids, lacking mitochondria were classified as the most primitive protozoans. The current thinking is that these protozoans lost their mitochondria. What kind of evidence supports this approach?

2.Most fungi and many protists can reproduce sexually and asexually. From a survival perspective, what are the advantages and disadvantages of each type of reproduction?

3.Fungi were once considered plants that do not perform photosynthesis. Now fungi have their separate kingdom: Fungi. Which characteristics of fungi led to the reclassification? Describe at least 3 structural characters, one phylogenetic evidence and one metabolic characteristic that distinguish fungi from plants.

Explanation / Answer

1. According to the endosymbiotic theory, it is proposed that organelles like mitochondria & chloroplasts originated as bacterial endosymbionts. The theory proposes that chloroplasts and mitochondria evolved from certain types of bacteria that protozoan cells engulfed through phagocytosis. These protozoan cells and the bacteria trapped inside them entered a symbiotic relationship. Hence, it supports the fact that early protozoans are devoid of mitochondria.

TYPE OF REPRODUCTION

ADVANTAGE

DISADVANTAGE

SEXUAL

1-It leads to the mixing of genes in the gene pool; thereby increasing the number of variations in the gene pool.

1-Requires both sexes to participate.

In absence of one sex, it cannot occur.

2- It leads to a greater genetic diversity, due to shuffling of the mutations from one generation to another.

2- a complex process, requiring a lot more energy than asexual reproduction.

ASEXUAL

1-Asexual reproduction is less complex & requires lesser energy as compared to sexual reproduction.

1-It does not lead to increase in genetic diversity.

2- There is no problem regarding environment; with sexual reproduction, offsprings may not survive when they are dealing with a harsh environment. So in harsh conditions, fungi reproduce asexually

2- It produces less variations in the offsprings; all of them are more or less identical- this may lead to a barrier in adaptation of the fungal colony to environmental changes.

3- It is a rapid process & can be used by fungi to reproduce quickly in order to establish a new colony.

3. It may lead to overcrowding in a fungal colony.

Many fungi are superficially plant-like organisms. They grow visible structures that resemble plants or plant parts. Fungi however are different from plants. The major differences are-
1- They have chitin in their cell-wall, a complex polysaccharide which the plants do not possess.

2- They are achlorophyllous organisms.

3- They are not producers of food, unlike plants they absorb nutrients from the soil.

These differences led to the reconsideration of the kingdom classification & allowed Fungi to have a separate kingdom in the new system of classification.

DIFFERENCE BETWEEN FUNGI & PLANTS:

CHARACTERISTICS

PLANTS

FUNGI

Structural- CELL WALL

Made of cellulose, hemicellulose, lignin, suberin etc.

Made of primarily chitin

Structural- CHLOROPHYLL

Most plants contain a green pigment called chlorophyll that helps in photosynthesis.

Absence of chlorophyll; they are saprophytic in nature & absorb nutrients from soil instead of food-making.

Structural- HYPHAE or MYCELIUM

No presence of hyphae

Hyphae is the structural unit of fungi.

Phylogenetic evidence-

Fungi are more closely related to animals than plants. PHYLOGENETIC EVIDENCE include analysis of protein sequences biosynthetic pathways, cytochrome systems, mitochondrial genetic material, mode of nutrition & storage of nutritive materials- all these analysis indicate a major difference between plants & fungi

Metabolic characteristics

Plants generally store food in the form of starch

Fungi store food in the form of glycogen, a trait it shares with the animals.