03. Evolution and Diversity of Organisms

Question 1

Explain the nature of the first atmosphere

Answer 1

*The first atmosphere was thick with water vapour, along with various compounds released by volcanic eruptions, including nitrogen and its oxides, carbon dioxide, methane, ammonia, hydrogen and hydrogen sulphide.

*The first atmosphere had little oxygen.

*Later earth was cooled down and the water vapour condensed into the ocean.

Question 2

Along with earth’s reducing atmosphere, what favored the synthesis of organic molecules, essential for the origin of life?

Answer 2

*Volcanic eruptions ( V A L H E)

*lightening

*extreme UV radiation

*hydro thermal vents

*alkaline vents

Question 3

Name the four main stages of producing the first cells during biochemical evolution

Answer 3

-Atmospheric conditions of early earth facilitated the abiotic synthesis of small organic molecules such as amino acids and nitrogenous bases from inorganic molecules

-Polymerization of the above small organic molecules leads to the formation of organic macromolecules.

-Organic macromolecules were packed into membranes, to produce protocells

-Nucleic acids gained self replicating capability, which made inheritance possible for the cells.

Question 4

What did haldane suggest?

Answer 4

Haldane suggested that the early oceans were a solution of organic molecules “primitive soup” in which life arose.

Question 5

What are the five stages of the evolution of the biological diversity?

Answer 5

1. Biochemical evolution
2. Origin of the protocell
3. Origin of the photosynthetic organisms
4. The origin of the first eukaryote
5. Diversification of the eukaryotes

Question 6

What are the four geographical eons?

Answer 6

Hadean

Archaean

Proterozoic

Phanerozoic

Question 7

What are the three different eras?

Answer 7

Palaeozoic

Mesozoic

Cenozoic

Question 8

What are the events taking place in the hadean era?

Answer 8

Origin of the earth

Question 9

What events take place during the archean era?

Answer 9

Oldest known rocks on Earth’s surface

Oldest fossils of cells (prokaryotes) appeared

Concentration of atmospheric oxygen begins to increase

Question 10

What events take place during the Proterozoic era?

Answer 10

Diverse algae and soft-bodied invertebrate animals appeared

Oldest fossils of eukaryotic cells appeared

Question 11

What events take place during Paleozoic era?

Answer 11

• Sudden increase in diversity of many animal phyla
• Marine algae becomes abundant; colonization of land by diverse fungi, plants,
and animals
• Diversification of vascular plants
• Diversification of bony fishes, first tetrapods and insects appeared
• Amphibians dominated
• Extensive forests of vascular plants
• First seed plants appeared
• Origin and radiation of reptiles
• Origin of most present-day groups of insects
• Extinction of many marine and terrestrial organisms
• Diversification of early vascular plants

Question 12

What events take place during Mesozoic era?

Answer 12

• Cone-bearing plants (gymnosperms) dominated
• Dinosaurs evolved, radiated
• Origin of mammals
• Gymnosperms continued as dominant plants, dinosaurs dominated, abundant and diverse
• Flowering plants (angiosperms) appeared and diversified, many organisms including dinosaurs become extinct

Question 13

What events take place during the Cenozoic era?

Answer 13

• Major radiation of mammals, birds, and pollinating insects

• Dominance of angiosperm increased and their radiation continued, radiation of most present day mammalian orders

• Origins of many primate groups, continued radiation of mammals and angiosperms, earliest direct human ancestors

• Appearance of bipedal human ancestors

• Origin of genus Homo

Question 14

What are the theories of evolution?

Answer 14

• Theory of Lamarck.
• Darwin - Wallace theory (Theory of Natural selection)
• Neo Darwinism

Question 15

What hypothesis does the theory of Lamarck include?

Answer 15

1. Use and disuse
2. Inheritance of acquired characteristics

Question 16

What does use and disuse include?

Answer 16

The parts of the body that are used extensively become larger and stronger.

If not used, they deteriorate.
e.g.- Giraffe stretching its neck to reach leaves on higher branches.

Question 17

What does the inheritance of the acquired characteristics include?

Answer 17

Organism acquired adaptation during their life time according to the needs of enviro off spring is better adapted to
live in that environment e.g. long muscular neck of the giraffe had evolved over many generations as giraffes stretch their necks even higher

Question 18

What were the observations of Darwin in his theory of inheritance?

Answer 18

The populations of a species vary in characteristics among their inheritance traits.

Each species produces more offspring than their environment could accommodate.

Question 19

What were the interpretations of Darwin in his theory of inheritance?

Answer 19

Certain traits of a population which are capable of exhibiting qualities for better survival and their reproduction can produce more offspring.

Variation in abilities for survival and production among a population may enhance the abundance of favorable characteristics in that population.

Question 20

What are the favorable traits for survival and reproduction?

Answer 20

• Escaping from predators - defense

• Tolerating physical conditions – stress conditions

• Obtaining food

• Resistance against disease

• Fertilizing probability
• Number of offspring produced

Question 21

Name the process of natural selection in four steps

Answer 21

(One Virgin Cooks Nutella)

Over production

Variation

Competition and survival of the fittest

Natural selection of favorable traits

Question 22

What does Neo-Darwinism include?

Answer 22

Neo-Darwinism generally denotes the integration of Charles Darwin’s theory of natural selection, Mendelian genetics as the basis for biological inheritance and knowledge of population genetics.

Question 23

What are the two methods of classification?

Answer 23

Natural Classification
Artificial Classification

Question 24

What are pre-selected unifying characters artificial classification is based on?

Answer 24

• The characters are selected first according to convenience and organisms are
grouped based on the selected criteria
• Evolutionary relationships are ignored
• Only system used before 18th century
• Easy to use, easy to expand by adding more groups

Question 25

Write examples for artifical classfication

Answer 25

Plants can be classified as cereals, ornamental plants, medicinal plants, poisonous plants etc. Animals can be classifi ed as two legged, four legged, six legged, eight legged etc

Question 26

Write the characteristics of natural classification

Answer 26

• Represent s evolutionary relationships based on phylogeny- evolutionary history
of a species or groups of species
• Systems developed after then study of evolution.
• Based on many characteristics. ( Characteristics used can be morphological, anatomical, cytological or molecular
biological such as DNA and RNA base sequences)

Question 27

Give examples for natural selection

Answer 27

Plants can be classifi ed into phyla; Bryophyta, Lycophyta, Pterophyta, Cycadophyta, Coniferophyta and Anthophyta etc. Animals can be classified into Cnidaria, Platyhelminthes etc.

Question 28

What were the early classfication systems based on?

Answer 28

they were all artificial systems and were mostly based on human uses.

Question 29

How did aristotle divide animals scientifically?

Answer 29

He divided organisms into plants and animals. Animals were further classified according to criteria such as mode
of locomotion, reproduction and presence or absence of red blood cells.

Aristotle’s pupil Theophrastus classified plants according to habit.

e.g. trees, shrubs and herbs, and according to lifespan e.g. annuals, biennials and perennials.

Question 30

Who introduced binomial nomenclature?

Answer 30

Carolus Linnaeus introduced binomial nomenclature

Question 31

What is included in binomial nomenclature?

Answer 31

He classified about 6,000 plants into a hierarchical order of taxa, classification level such as; Species, genus, order, and class.

His classification of flowering plants was based on the number of stamens and styles of flower.

He identified two kingdoms of organisms; plants and animals.

Question 32

What did Ernest Haeckel introduce?

Answer 32

He introduced a third kingdom: Protista.
He also introduced the taxon Phylum and classified many organisms

Question 33

how did biologists identify prokaryotic and eukaryotic cellular organization

Answer 33

With the discovery of the electron microscope

Question 34

What did Robert Whittaker introduce?

Answer 34

He introduced the five kingdom system of biological classification; Monera, Protista, Fungi, Plantae and
Animalia.

His classification was based on the nature of cellular organization, unicellular or multicellular and mode of nutrition.

Question 35

Who introduced the 3 domain system?

Answer 35

Carl Woese

Question 36

How did the first major split in the history of life occur?

Answer 36

In this tree of life the first major split in the history of life occurred when bacteria diverged from others

Eukarya and Archea are mostly related to each other than bacteria.

Question 37

What is the present system of classification based mainly on?

Answer 37

The present system of classification is mainly based on the rapid advance of molecular biology and the new information on the evolutionary relationships of organisms.

Question 38

what factors are important taxonomic criteria in modern systematics?

Answer 38

• the sequence of bases of DNA of important genes
• the sequences of bases of DNA of mitochondria and chloroplasts
• the base sequence of ribosomal RNA
• the sequence of amino acids in common proteins
• the molecular structure of cellular components

Question 39

what group is an artificial group including organisms which have different evolutionary origins.

Answer 39

Kingdom Protista

Question 40

What is an artificial group considered separately?

Answer 40

Viruses do not have cellular organization, and therefore do not belong to any of the kingdoms

Question 41

Give examples for taxon

Answer 41

Panthera is a taxon at the Genus level/ rank
Mammalia is a taxon at the Class level/ rank

Question 42

Under the hierarchical system there are levels/ ranks of taxa. What are they?

Answer 42

Each Domain is divided into kingdoms. A Kingdom is divided into phyla (singular phylum), phylum into classes .etc. Many of these categories may also be subdivided.

(e.g. Super class, Sub-family, Subspecies, etc.)

Question 43

When does the the number of shared characteristics among the members in the taxa increase?

Answer 43

From domain to species

Question 44

When does the number of individuals in the taxon increase?

Answer 44

From species to domain

Question 45

Name some common names do not actually reflect the kind of organism they signify

Answer 45

Jelly fish (a Cnidarian)
Cray fish (a Crustacean)
Silver fish (an insect)
Star fish (an Echinoderm)

Question 46

Describe the features of binomial nomenclature?

Answer 46

First is the generic name, to which the species belongs and the second is a specific epithet, the unique for each species within the genus.

Generic name is usually a noun and the specific epithet an adjective describing a particular feature.

e.g. Homo sapiens- Homo means man, sapiens means intelligent

Related species have the same generic name with different specifi c epithets.
e.g. Dipterocarpus zeylanicus and Dipterocarpus grandifl orus
Dipterocarpus zeylanicus means fruit with two wings, and endemic to Sri Lanka.
Dipterocarpus grandiflorus means fruit with two wings and having large fl owers.

Question 47

What are some important rules of nomenclature?

Answer 47

• Two species of organisms cannot have the same name.

• Each species has a generic name and a specific epithet, both together forming the
species name or scientific name.

• The Name should be made up of Latinized words written in the Roman script.

• It should be underlined when hand written and italicized when printed.

• The first letter of the generic name must be capitalized the and specific epithet
must be in simple letters

In scientific writing, the name of the author who gave the name is indicated by a capital
letter, an abbreviation or full word at the end of the name, which is not Latinized.

A third word can be used to represent a subspecies or a variety

Question 48

What are the uses of keys in binomial nomenclature?

Answer 48

• Used to group organisms and identify them
• Keys do not show the evolutionary relationships
• The Commonly used key is the dichotomous key
• Some examples are given below

Question 49

What are the three domains?

Answer 49

a) Domain – Bacteria

b) Domain –Archaea

c) Domain –Eukarya

Question 50

What are domain eukarya’s 4 kingdoms?

Answer 50

Kingdom - Protista

Kingdom - Fungi

Kingdom - Plantae

Kingdom - Animalia

Question 51

What are the kingdoms of domain bacteria?

Answer 51

kingdom bacteria

Question 52

What is domain archaea’s kingdom?

Answer 52

Kingdom Archaebacteria

Question 53

What are the key characteristics of domain bacteria?

Answer 53

• They are prokaryotic

• They are unicellular, colonial, filamentous

• Most of them are found in size between 0.5 to 5µm

• Well adapted to most of the ‘normal’ habitats (both land and water)

• Most of them contain peptidoglycan in their cell walls

• According to the amount of peptidoglycan present in the cell wall they are
classified as Gram positive and Gram negative bacteria

• Most of their cell walls are surrounded by a sticky layer of polysaccharides or
proteins called capsule

• Most of them have flagella for motility. Bacterial flagellum differs from
eukaryotic flagellum as they are not covered by a plasma membrane and absence
of 9+2 structure of microtubules.

• Possess diverse nutritional modes-Autotrophs, heterotrophs

• Posses diverse metabolic modes- obligate aerobes, obligate anaerobes, facultative
anaerobes, etc.

• Some are capable of performing nitrogen fixation- e.g. Rhizobium sp., some
cyanobacteria

• Rapid reproduction by binary fission. Some perform conjugation as a sexual
method.

• Certain bacteria use bacterial chlorophyll as a photosynthetic pigment

Question 54

What are the key characteristics of cyanobacteria?

Answer 54

• Prokaryotic organisms

• Photosynthetic

• Most are unicellular and oxygen generating and solitary. But some are linked to
form filaments or colonies sheathed in mucous

• Some have the ability of fixing atmospheric nitrogen

Question 55

What are the key characteristics of domain archaea?

Answer 55

They are prokaryotic and unicellular.

• They lack peptidoglycan in their cell walls which are made up of proteins and
polysaccharides

• The size of most of them is between 0.5-5 m

• They include extreme halophiles and extreme thermophiles

• Some Archaebacteria live in more moderate environments-Methanogens

• Other species inhabits the anaerobic guts of cattle, termites and other herbivores

Question 56

what are the key characteristics of Domain Eukarya?

Answer 56

• They are Eukaryotic

• Vary in size

• Most of them are multicellular

• Habitats are diverse

• Diverse in nutrition

• Mostly aerobes

• Most of them exhibit sexual reproduction (some protists are only known
to reproduce asexually)

Question 57

What are the key characteristics of kingdom protista?

Answer 57

• Most of them are unicellular, although there are some colonial and multi cellular
species

• It is a polyphyletic group (originated from more than one ancestor) and an
artificial group in classification.

• Found in freshwater, marine and damp soil, some are symbionts.

• Unicellular, colonial or multicellular.

• Some are photoautotrophs, some are heterotrophs and some are mixotrophs
(combination of photoautotrophic and heterotrophic nutrition)

Question 58

Write the characteristics of Euglena

Answer 58

• Unicellular, lack cell wall and pellicle present.

• Chloroplasts are present.

• They have one or two flagella

• They have eye spot

• Contractile vacuole is present

• They have a pocket at one end of the cell from which one or
two flagella emerged

Question 59

What are the characteristics of paramecium ?

Answer 59

• Habitat is freshwater

• Lack cell wall but pellicle is present, unicellular

• Cilia may completely cover the cell surface

• They have two types of nuclei- mega nucleus
and micronucleus

• Contractile and food vacuoles are present

• Oral groove is present

Question 60

Write the features of amoeba

Answer 60

• Aquatic (marine and freshwater) forms are free
living others are parasitic.

• Lack cell walls, unicellular organisms

• They form pseudopodia which are used to
locomote and feed

• They do not have definite shape.

• Food vacuoles are present

Question 61

Write the features of Ulva

Answer 61

• Macroscopic marine forms.

• Cell wall present

• Multicellular thallus differentiated into leaf like
blades and root like holdfast.

• Green in colour (green algae)

Question 62

Write the features of Gelidium

Answer 62

• Marine.
• Cell walls present
• Multicellular thallus with hold fast.
• It is greenish red in colour (red algae)

Question 63

Write the features of sargassum

Answer 63

• Marine

• Comparatively larger and complex

• Thallus is plant- like; it consists of a root
like holdfast ,stem like stipe and leaf like
blade.

• Multi cellular, thallus is supported by gas
filled bulb shape floats.

• Appear in olive green or brown colour (brown algae)

Question 64

Write the features of diatoms

Answer 64

• It is aquatic (fresh water and marine)

• Unicellular, having glass like, wall
consists of two parts that overlap
(presence of silica)

• Highly diverse group regarding the shape
and markings in the surface

• Golden brown in colour (golden brown
algae)

Question 65

Where did the members of the kingdom Plantae evolve from?

Answer 65

a group of chlorophytes/ green algae

Question 66

What are the features of plants lacked by chlorophyte algae?

Answer 66

walled spores produced in sporangia
multicellular gametangia
dependent embryo and apical meristem

Question 67

What type of organisms are most plants?

Answer 67

Most of them are terrestrial organisms

Question 68

What are the two plant groups that can be distinguished based on the presence or absence of an extensive system of vascular tissue?

Answer 68

Vascular Plants
Non-vascular Plants

Question 69

What are phylum of non-vascular plants?

Answer 69

• Phylum Bryophyta

• Phylum Hepatophyta- Marchantia

• Phylum- Anthocerophyta- Anthoceros

Question 70

Write examples for a plant found in Phylum Bryophyta

Answer 70

• Mosses- Pogonatum

Question 71

Write examples for plants found in Phylum Hepatophyta

Answer 71

Marchantia

Question 72

Write examples for plants found in Phylum Anthocerophyta?

Answer 72

Anthoceros

Question 73

What are the phylum of vascular seedless plants?

Answer 73

• Phylum Lycophyta

• Phylum Pterophyta

Question 74

Write examples for phylum lycophyta?

Answer 74

Selaginella

Question 75

Write examples for phylum Pterophyta?

Answer 75

Nephrolepis

Question 76

What are the phylum of vascular seed plants?

Answer 76

They are Gymnosperms

Phylum – Cycadophyta (Cycas sp.)
,
Phylum- Coniferophyta (Pinus )

Phylum – Gnetophyta (Gnetum )

Angiosperms- Phylum Anthophyta (all flowering plants)

Question 77

Give examples for phylum Cycadophyta

Answer 77

(Cycas sp.)

Question 78

Give examples for Phylum Coniferophyta

Answer 78

Pinus

Question 79

Give examples for Phylum Gnetophyta

Answer 79

Gnetum

Question 80

Give examples for Angiosperms Phylum

Answer 80

Anthophyta (all flowering plants)

Question 81

How do you distinguish between vascular and non-vascular plants?

Answer 81

One way to distinguish a group of plants is to see whether or not they have an extensive system of vascular tissue that transport water and nutrients throughout the plant body.

Question 82

What are Non vascular plants are informally named as ?

Answer 82

Bryophytes.

Question 83

Give examples for bryophytes

Answer 83

Marchantia
Pogonatum
Antheroceros

Question 84

What are some traits bryophytes share with vascular plants?

Answer 84

Bryophytes share some derived traits with vascular plants

Question 85

What innovations do bryophytes lack but vascular plants possess?

Answer 85

Bryophytes lack many innovations of vascular plants such as presence of true stems, roots and leaves

Question 86

What are the characteristic features of bryophytes?

Answer 86

• Especially common in moist terrestrial places.

• Haploid gametophyte is dominant stage of the life cycle, photosynthetic and
independent.

• Gametophytes are differentiated into ‘leaves’, ‘stems’ and rhizoids. They have
no vascular tissues. Archegonia and antheridia are typically carries on separate
female and male gametophyte. Therefore gametophyte is dioecious.

• Male plant produces flagellated sperm which can swim through a fi lm of water
for fertilization.

• Sporophytes are usually green and photosynthetic when young. However, they
are not independent. They attach to their parental gametophytes and absorb
nutrients and water from the female gametophyte.

• Sporophytes have specialized pores called stomata which are also found in all
vascular plants.

• They are homosporous.

Question 87

What percentage of vascular plants cover the existing plant species?

Answer 87

Vascular plants cover about 93% of the existing plant species.

Question 88

What phylum of seedless vascular plants share a more recent common ancestor with seed plants?

Answer 88

pterophytes share a more recent common ancestor with seed plants.

Question 89

What are the evidences for plant evolution during Devonian and Carboniferous periods?

Answer 89

Fossils and living seedless vascular plants provide evidence

Question 90

What do the ancestors of vascular plants already have similar to modern vascular plants?

Answer 90

The ancestors of vascular plants already have had some derived traits of modern vascular plants

Question 91

What do ancestors of vascular plants lack compared to modern vascular plants?

Answer 91

they lack roots and some other adaptations.

Question 92

What do fossils suggest about the ancestors of vascular plants?

Answer 92

Fossils suggest that, the ancestors of vascular plants had gametophyte and sporophytes that were about equal in size.

However among the living vascular plants sporophyte generation is large and more complex.

For example in ferns, leafy plants are the sporophytes

Question 93

What are the two types of vascular tissues vascular plants have?

Answer 93

Xylem and Phloem

Question 94

What are the two types of vascular tissues vascular plants have?

Answer 94

Xylem and Phloem

Question 95

What does the xylem consist of?

Answer 95

tracheids
fibers
parenchyma cells

Question 96

What is the function of parenchyma cells in the xylem?

Answer 96

• conducting water and minerals.

Question 97

How are the cell walls of tracheids and fibers strengthened?

Answer 97

by the polymer lignin

Question 98

What are the functions of polymer lignin in xylem?

Answer 98

These tissues permit plants to grow tall.

This may facilitate them to obtain a high amount of light for photosynthesis and ease the spore dispersal.

Question 99

How is phloem arranged?

Answer 99

this tissue has cells arranged in tubes

Question 100

What does the phloem distribute?

Answer 100

They distribute sugars, amino acids and other organic products among different parts of the plant

Question 101

What are the functions of roots?

Answer 101

Roots are organs that absorb water and nutrients from the soil.

They anchor the plants and allow the shoot system to grow taller.

They are to replace the rhizoids seen in bryophytes.

Question 102

What do root tissues of living plants resemble in early vascular plants?

Answer 102

Root tissues of living plants resemble stem tissues of the early vascular plants preserved in fossils

Question 103

What are the 2 types of leaves?

Answer 103

microphylls
megaphylls

Question 104

What are the differences between microphylls and megaphylls?

Answer 104

Microphylls are single veined and smaller in size while megaphylls are large, flattened with branched veins

Question 105

What is the reason for megaphylls having branched vascular tissues?

Answer 105

Leaves with branched vascular tissues increase the surface area for efficient photosynthesis

Question 106

Why are most seedless vascular plant species known as homosporous?

Answer 106

Most seedless vascular plant species produce one type of sporangium and one type of spores. Therefore, they are known as homosporous.

Question 107

What is the heterosporous condition?

Answer 107

Some plant species produce two types of sporangia and produce two kinds of spores called mega spores and microspores. This condition is known as heterosporous.

Question 108

What do mega spores and microspores develop into?

Answer 108

Mega spores develop into female gametophyte

Microspores develop into male gametophyte

Question 109

Write the characteristic features of lycophyta

Answer 109

• Lycophytes are terrestrial and some are epiphytes.

• The dominant plant is sporophyte.

• They produce upright stems and ground hugging stems.

• In upright stems small leaves can be found.

• Ground hugging stems produce dichotomously branching roots.

• They have strobili. In many club mosses and spike mosses sporophylls are
clustered into club shaped cones/ strobili.

• They are homosporous or heterosporous

• Spike mosses are usually relatively smaller and often grow horizontally.

• All Club mosses are homosporous;

• All Spike mosses are heterosporous.

• In some species the tiny gametophyte live above the ground and are photosynthetic. Others live below the ground and
are nourished by symbiotic fungi.

Question 110

Give examples for club mosses that are homosporous

Answer 110

Lycopodium sp.

Question 111

Give examples for Spike mosses that are heterosporous

Answer 111

e.g. Selaginella

Question 112

What are the characteristic features of phylum pterophyta?

Answer 112

• Most sporophytes have rhizome (an underground stem)

• At the tip of the rhizome they produce leaves, called fronds

• Many fronds are highly dissected and feathery.

• All species are homosporous which develop into a bisexual gametophyte.

• Sporophytes are dominant

Question 113

Give an examples for dominant sporophytes

Answer 113

e.g. Nephrolepis

Question 114

What category of plants represent the vast majority of living plant species?

Answer 114

Seed plants

Question 115

How are seed plants categorized based on the absence or presence of enclosed chambers in which seeds mature?

Answer 115

1. Gymnosperms
2. Angiosperms

Question 116

Why are Gymnosperms referred to as “naked seed plants”?

Answer 116

Gymnosperms are “naked seed” plants as their seeds are not enclosed in chambers.

Question 117

Why are angiosperms called a “seed plant group”?

Answer 117

Angiosperms are “seed plant” group accommodating all flowering plants

Angiosperm seeds develop inside chambers called ovaries; which originate within flowers and mature into fruits.

Question 118

What are the significant features of seed plants?

Answer 118

1. Production of seed
2. Reduced gametophyte
3. Heterospory
4. Production of ovules and eggs
5. Production of pollen and sperms

Question 119

What are the two parts of a seed?

Answer 119

A seed consists of an embryo and endosperm

Question 120

What is the function of endosperms?

Answer 120

Endosperms supply food to the embryo

Question 121

What is the endosperm surrounded by?

Answer 121

This endosperm is surrounded by a protective coat which is known as seed coat

Question 122

What happens when seeds mature?

Answer 122

When seeds are mature they can be dispersed through various dispersal methods.

Question 123

What adaptations do seeds give seed plants?

Answer 123

Seeds are key adaptations that help seed plants to become the dominant producers on land and to exhibit the vast plant diversity of today

Question 124

Unto what extent did the evolutionary trend of gametophyte reduction extend to?

Answer 124

The evolutionary trend of gametophyte reduction continued further in the vascular plants and led to seed plants

Question 125

Why are gametophytes of seed vascular plants not visible to the naked eye?

Answer 125

The gametophyte of seed vascular plants is not visible to the naked eye because they are mostly microscopic.

Question 126

What is the arrangement of the tiny gametophyes?

Answer 126

Tiny gametophytes develop from spores and are retained within the sporangia of sporophyte

Question 127

What is the function of the arrangement of tiny gametophytes?

Answer 127

This arrangement protects the gametophyte from environmental stresses

Question 128

What is the function of the moist reproductive tissues of the sporophyte?

Answer 128

The moist reproductive tissues of the sporophyte shield the gametophyte from UV radiation and protect them from drying out

This relationship also enables the dependent gametophyte to obtain nutrients from the sporophyte

Question 129

What do megasporangium and microsporangium contain?

Answer 129

Each megasporangium has a single functional megaspore and each microsporangium contains a large number of microspores.

Question 130

What is the uniqueness of seed plants?

Answer 130

Seed plants are unique in retaining the megasporangium within the parent sporophyte

Question 131

What does the integument envelope do?

Answer 131

A layer of sporophyte tissue called integument envelops which protects the megasporangium

Question 132

What occurs inside each ovule?

Answer 132

Inside each ovule female gametophyte develops from a megaspore and produces one or more eggs.

Question 133

What does the microspore develop into?

Answer 133

into pollen grain that consists of a male gametophyte enclosed within the pollen wall

Question 134

What are the features of the pollen wall?

Answer 134

The wall of the pollen is tough as it is made up of the polymer sporopollenin, which protects the pollen grain during pollination.

Question 135

What happens when the pollen germinates?

Answer 135

it gives rise to a pollen tube that discharges sperm (male gametes) into the female gametophyte
located within the ovule

Question 136

What do some gymnosperms retain?

Answer 136

Some gymnosperms retain the ancient fl agellated condition, however fl agella
have been lost in the sperm of most gymnosperms and all angiosperms.

Question 136

What do some gymnosperms retain?

Answer 136

Some gymnosperms retain the ancient flagellated condition, however flagella
have been lost in the sperm of most gymnosperms and all angiosperms.

Question 137

What is present inside a pollen grain?

Answer 137

Inside a pollen grain, a sperm producing male gametophyte is present.

Question 138

Why does the sperms of seed plants do not require motility?

Answer 138

The sperms of
seed plants do not require motility as they are carried directly in to the eggs by pollen
tubes.

Question 138

Why does the sperms of seed plants do not require motility?

Answer 138

The sperms of
seed plants do not require motility as they are carried directly in to the eggs by pollen
tubes.

Question 139

What are the features of the phylum Gnetophyta?

Answer 139

Only gymnosperms have vessels in xylem
• Leaves of gymnosperms look like those of the fl owering
plants. Their seeds, look like fruits of angiosperms.

Question 140

What are the features of the phylum cycadophyta?

Answer 140

They have palm like leaves and large
cones
• They have fl agellated sperms similar
to those of seedless vascular plants
e.g. Cycas

Question 141

What are the features of the phylum coniferophyta?

Answer 141

e.g: Pinus
• Large trees are included such as Cyperes and Red
woods.
• In conifers two types of spores are produced by
separate cones.

Question 142

What are the features of phylum anthophyta?

Answer 142

• Stamens produce microspores and these microspores develop into pollen grains
• These pollen grains contain male gametophyte/ gametes
• Carpels produce megaspores and these megaspores produce female gametophytes/
embryo sac
• Seeds are enclosed within the carpels
• Production of fruit

Question 143

What is one of the unique features of the phylum anthophyta?

Answer 143

Seeds are protected by fruits which help in their dispersal. This is one of the unique features of phylum Anthophyta

Question 144

What does a fruit typically consist of?

Answer 144

A fruit typically consists of a fertilized ovary and sometimes include other persistent fl oral parts. After
fertilization, the ovary wall thickens and develops into fruit. Ovules develop as
seed of the fruit

Question 144

What does a fruit typically consist of?

Answer 144

A fruit typically consists of a fertilized ovary and sometimes include other persistent fl oral parts. After
fertilization, the ovary wall thickens and develops into fruit. Ovules develop as
seed of the fruit

Question 145

What is the function of the fruit?

Answer 145

The fruit protects dormant seeds and aid in their dispersal.

Question 145

What is the function of the fruit?

Answer 145

The fruit protects dormant seeds and aid in their dispersal.

Question 146

Based on the number of cotyledons in the embryo, what are the two groups of angiosperms?

Answer 146

1. Monocotyledons- species with one cotyledons
2. Dicotyledons- species with two cotyledons

Question 147

What are the features of monocot vs dicot?

Answer 147

The embryos have only one cotyledon in Monocotydonae whereas Embryos have two cotyledons in class Dicotyledonae

Fibrous root system in Monocotydonae where as tap root system is found in class Dicotyledonae

Parallel veins in leaves in Monocotydonae class and reticulate veins in leaves can be seen in class Dicotyledonae

Flower parts are trimerous in Monocotydonae class and flower parts are pentamerous/tetramerous

Perianth present in flowers (No distinct calyx and corolla) in Monocotydonae class and Distinct calyx and corolla present
in flowers in Dicotyledonae class

Pollen grains are with one opening/ aperture in Monocotydonae class and Pollen grains are with three
openings/ apertures in Dicotyledonae class

Vascular bundles in the stem do not have cambia and are scattered (grasses, coconut, rice) in Monocotydonae plants and Vascular bundles in the stem have cambia and arranged in a ring (e.g. Rose, shoe flower, cucurbits) in Dicotyledonae class

Question 148

What are the characteristics of fungi?

Answer 148

• Eukaryotic
• Cell walls are made up of chitin a strong but fl exible polysaccharide.
• They are absorptive and heterotrophs - many of them secrete extra
cellular enzymes which aid in the breaking down of complex molecules
into small molecules.
• Different species live as decomposers, parasites or mutualistics.
• Few are unicellular, others forming multicellular fi laments called hyphae .
• Septa can be found in hyphae. (division of hyphae into cells by septa –
cross walls).
• Septum has a hole which enables the movement of mitochondria, ribosomes,
nuclei etc.
• Fungi lack septa are known as coenocytic fungi (with many nuclei)
• Fungal hyphae produce mycelium
• Some fungi produce haustoria ( to penetrate and absorb or exchange
nutrients between plants and the fungi)
• Multicellular fungi produce mycelia. ( a network of branched hyphae
adapted for absorption of nutrition)
• They show sexual and asexual reproduction.
• They produce spores.

Question 149

What are the characteristics of the phylum Chytridiomycota?

Answer 149

e.g.: Chytridium
• Aquatic or terrestrial .
• Some are decomposers while others are parasitic.
• Multicellular or unicellular when multicellular it is coenocytic.
• They produce zoospores which are fl agellated.
• Cell walls are made up of chitin.
• Some of them form colonies with hyphae while others exit as single
spherical cell.

Question 150

Characteristics of phylum zygomycota?

Answer 150

e.g. Mucor , Rhizopus
• Most of them are saprotrophs and some of them are parasites or commensals.
• Mycelium is coenocytic and aseptate. Septa found only where reproductive cells
are formed.
• Asexual reproduction: Produce sporangia in which genetically identical haploid
spores are produced. Also by endospores produced in sporangia.
• Sexual reproduction: A Zygosporangium is produced which is a sturdy structure
produced by plasmogamy and karyogamy. Zygosporangium is resistant to
unfavorable environmental conditions.
o Zygosporangium is a multinucleated structure which is resistant
to drying and freezing.
o They are metabolically inactive in adverse environmental
conditions.
• Zygosporangium produces genetically diverse haploid spores when
environmental conditions are favourable.

Question 151

Features of Ascomycota?

Answer 151

e.g. Aspergillus, Saccharomyces, Penicillium
• Marine or freshwater or terrestrial
• Parasitic or symbiotic.
• Most of them are decomposers.
• Unicellular or fi lamentous, multicellular.
• In asexual reproduction conidia are produced at the tip of the conidiphores which
are specialized hyphae. (Exospores in clusters or chains)
• In sexual reproduction fusion of sexually differentiated gametangia takes
place and produce sac like structure called asci.
• Ascospores are produced within asci. Generally there are eight ascospores are
produced in each ascus.
• Most of these fungi produce ascocarps enclosing asci.

Question 152

Features of phylum basidiomycota?

Answer 152

e.g. Agaricus, Puffballs, Shell fungi
• They are Terrestrial.
• They are major decomposers and some are symbionts.
• Filamentous with septae and dikaryotic.
• Mycelium is the dominant stage of the life cycle.
• They produce fruiting bodies called basidiocarps during sexual
reproduction. Produce basidia on the gills of the basidiocarp.
• Produce basidiospores on basidium and exogenous.

Question 153

Features of kingdom animalia?

Answer 153

Multicellular
• Heterotrophic eukaryotes- they ingest food and digest them in the body
using enzymes
• Cells of the animals are organized into tissues.
• Most of them reproduce by sexually.
• Some show radial symmetry and some others show bilateral symmetry.

Question 154

Features of kingdom cnidaria?

Answer 154

e.g. Hydra, Sea anemone, Obelia, Corals and Jelly fish

• Majority of them are marine, except a few fresh water species. Some are
macroscopic.
• Simple organization: diploblastic or just 2 body cell layers- an outer layers of
ectoderm and inner layer of endoderm sandwitched between these two layers is
a acellular layer of mesoglea
• They have a simple gastrovascular cavity which is a sac with a central digestive
compartment. This cavity is lined by endodermis with a single opening (mouth)
only.
• They show radial symmetry with two body forms polyp and medusa. Polyps
are cylindrical forms attached to the substrate by the aboral end of the body.
Tentacles are found around the mouth.
• Medusa resembles a fl attened mouth down version of the polyps and they are
free living.
• Some cnidarians exist only as polyps or only as medusa. Others have both polyp
and medusa forms in their lifecycles.
• Tentacles are armed with cnidocytes which functioning defense and capturing
prey.
• They have nematocysts which contain stinging thread

Question 155

Features of platyhelminthes?

Answer 155

e.g. Planaria, Taenia , Fasciola

• Commonly known as fl atworms.
• Free living (Planaria) or parasitic (fl ukes
and tapeworms).
• They are found in marine, fresh water and in
damp terrestrial habitats.
• Body is dorsoventrally fl attened. Some have
elongated tape like body forms without
true segmentation.
• Triploblastic with all three germ layers
(ectoderm, mesoderm and endoderm). Signs
of cephalization present but are not distinct.
• No body cavities, circulatory, respiratory and skeletal systems.The gaseous
exchange is by simple diffusion through body wall.
• Sensory organs are found only in free living examples. Eye spots are found in
the head.
• First appearance of little complex nervous and sensory system. A pair of anterior
ganglion and two longitudinal nerve cords on central nervous system.
• Appearance of separate organs for excretion: Nitrogenous excretory system
consists of protonephridia. These are a network of tubules with ciliated structures
called fl ame bulb. These are used to maintain the osmotic balance.
• They have incomplete digestive system only with mouth without anus. Branched
gastrovascular cavity is present for digestion. Some are having eversible pharynx.
• Free living examples have cilia for the locomotion.
• Some show asexual reproduction by regeneration. All are bisexual. Except tape
worms (Taenia). Others have cross fertilization which is internal. In parasitic
forms there are several larval stages, direct development in free living examples
without larval stages.

Question 156

Features of phylum nematoda?

Answer 156

e.g. round worms, hook worms, pin worms
• Most of them are free living in marine, few are fresh water and damp soil
environments and parasitic in plants and animals.
• They are bilateral symmetrical. Triploblastic with pseudocoelomic .Their body
forms are cylindrical with tapered ends. Body size varies from microscopic to
macroscopic. They do not show distinct cephalization and segmentation. The
sensory papillae are found on the anterior end of the body. Body is covered by
tough cuticle and undergoes ecdysis.
• No circulatory and respiratory systems. Gaseous exchange is by simple diffusion
through body wall. They have an Alimentary canal.
• Body wall is composed only of longitudinal muscles. They do not have special
locomotary structures. Longitudinal muscles in the body wall are involved in
locomotion.
• The Sexual reproduction is by internal fertilization. Sexes are separated and
females are larger than males.

Question 157

Annelida features?

Answer 157

e.g. Earthworms, Leeches and regworms.
• They can be marine, freshwater or in damp soil.
• They are segmented worms with cylindrical bodies
• They are Triploblastic.
• Coelom (true body cavity) is present for the fi rst time.
• The fi rst animals to show cephalization.
• Nervous system well developed; dorsal cerebral ganglion, ventral nerve chord,
circumenteric connectives.
• Clitellum, Parapodia, setae and suckers are found in some examples. Clitellum
is for external fertilization. Parapodia is used for locomotion and respiration.
Seate are present for locomotion and suckers for locomotion and ingestion in
ecto parasitic forms.

Question 158

Features of phylum mollusca?

Answer 158

e.g. Oysters, Clams, Slugs, Snails, Octupus, Squids, Chitons and tusks shells

• Majority are marine. Some inhabit freshwater and land. Some are bilateral
symmetrical and few are asymmetrical.
• They are soft bodied and non-segmented. Calcareous shell is secreted as a
protective exoskeleton. Coelomic.
• Body is divided into three parts:
o muscular foot is used for locomotion
o visceral mass contains most of the internal organs
o mantale is to secrete the shell
• Shell could be internal or external.
• Many molluscs possess radula (a minutely toothed, chitinous ribbon) in the
mouth for feeding.
• Most molluscs have separated sexes and their gonads are located in visceral
mass.

Question 159

Features of phylum arthropoda?

Answer 159

e.g. Insects, Spiders, Prawns, Crabs, Scorpions, Ticks, Mites, Millipedes
and Centipedes
• One of the most successful animal groups on earth with the highest number of
species. They live everywhere – air, water, soil
• They have segmented bodies with “jointed legs”
• They have a chitinous exoskeleton (skeleton on the outside) Because of
exoskeleton these animals can’t grow continuously and needs periodic molting
• The nervous system is well developed with primitive dorsal brain.
• The nerve cord is solid, segmented and ventrally located.
• They have many and varied sense organs.
• They have an open blood circulatory system; Blood is pumped by a heart into
the body cavities (haemocoel), where tissues are surrounded by the blood. No
capillaries.
• Respiration
• In aquatic animals- Gills
• In terrestrial animals- Tracheal system of chitinous tubes
• In arachnids - Book lungs
• Excretion is by Malphigian tubules They excrete uric acids
• Reproduction: Sexes separate [Dioecious]

Question 160

Features of phylum echinodermata?

Answer 160

• They are exclusively marine. Triploblastic and coelomic, slow moving or sessile.
• Adults are penta radial symmetrical without head and segmentation.
• Deuterostomes.
• Thin epidermis covers the endoskeleton of hard calcareous plates.
• Water vascular system is a network by hydraulic canals branching into tube feet
which function in locomotion and feeding.
• Digestive system is usually complete, but the mouth is on the underside and the
anus on the top surface of the animal.
• Circulatory system is reduced and closed without a heart. Sexes are separated
with external fertilization. Larval forms are bilaterally symmetrical.
• Well developed nervous system. Intelligent animals.

Question 161

Features of phylum chordata?

Answer 161

• Longitudinal, fl exible rod called notochord located between digestive tube and
nerve cord. It is extending from anterior to posterior providing support in at least
embryonic stage.
• Dorsal, hollow, single nerve cord located dorsal to the notochord.
• In all chordate embryos there are slits or clefts in pairs either side of pharynx
(pharyngeal sits) that opens to the outside of body. In terrestrial, adult chordates
it disappears and remains in the aquatic adults and larval forms of terrestrial
chordates as respiratory structures.
• Muscular tail that extends posterior to the anus present in the embryonic stages.
In some terrestrial adult it is reduced.

Question 162

Characteristic features of class Chondrichthyes

Answer 162

e.g. Skates, Sharks
• All are aquatic
• Skeleton composed predominantly of cartilage
• Fins for locomotion
• Caudal fi n is heterocercal.
• Gills without operculum.
• Body is covered with placcoid scales.
• Eggs are fertilized internally. Some are ovoviviparous and others are oviparous
or viviparous.
• Reproductive tract, excretory duct and digestive tract empty into the cloaca, a
common chamber that has a single opening to the outside

Question 163

Characteristic features of Class Osteichthyes

Answer 163

• All are aquatic
• Having a skeleton composed of bones.
• Gills are covered by a bony fl ap called operculum.
• Swim bladder for control the buoyancy.
• Caudal fi n is homocercal.
• Body is covered by fl atten bony scales called ctenoid and cycloid scales.
• Most are fertilized externally some have internal fertilization.
• Most species are oviparous.
e.g. Carp, Tuna,

Question 164

Characteristic features of Amphibia

Answer 164

• First animals to invade land but need water to complete life cycle, live in both
water and on land.
• They are found only on land or fresh waters. No marine species.
• First species to poses limbs, body is somewhat elevated by these limbs to help
locomotion in terrestrial environment.
• Some are limbless but some are tetrapods.
• Ectothermic- changes body temperature according to environmental temperature.
This restricts metabolism.
• Body is covered with thin, moist skin. No scales. Sensitive to environmental
changes.
• Nictitating membrane covers the eye and tympanic membrane is found behind
the eye.
• Most amphibians show external fertilization. Eggs without shells.
e.g. Toad, Frog, Ichthyophis

Question 165

Characteristic features of Reptilia

Answer 165

• They are the first animal to live a complete terrestrial life.
• Possess limbs for locomotion and digits.
• Body is covered with keratinized scales to prevent from desiccation and abrasion.
• Poses lungs for aerial respiration.
• They are ectothermic (cold blooded)
• Live in terrestrial and aquatic habitats.
• Internal fertilization. They lay shelled eggs (calcareous) on land.
e.g. Lizards, Snakes, Turtles, Crocodiles and Alligators

Question 166

Characteristic features of Aves

Answer 166

• Body is covered by keratinized feathers.
• Hind limbs are converted to fl ight.
• Many adaptations to help fl ying: light body, wings, bones with air cavities, high
metabolism, restrictions in body size
• They are having a beak without teeth.
• They are endothermic.
• Birds have colour vision and excellent eye sight.
• Internal fertilization, lay shelled eggs
e.g. Crow, Parrot, Humming birds, Eagles etc.