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Differences between gymnosperms and angiosperms, Practice Problems and FAQs

We live in a beautiful world surrounded by lots of organisms. Big animals are always fascinating and interesting to see, right?. The biggest animal existing now on the Earth is the blue whale and the one which is on the land is the elephant. We can not see these animals more often. But we might have seen the habitats and behaviour of these animals at least in televisions. Do you remember another biggest animal which became extinct? Yes, the dinosaurs!! They used to live during the Mesozoic era that includes three geologic time periods; Triassic, Jurassic and Cretaceous periods. Different species of dinosaurs lived during these periods. But the extinction of the last dinosaur happened during the Cretaceous period.

If you ever watched the Jurassic World movie, which depicts the life of dinosaurs, you might have observed their habitats too. What type of trees and plants can you observe around them? You can never find any trees like teak or gulmohar or plants like roses or bamboo, because these categories of plants are angiosperms. Do you know the reason for this? Why were angiosperms not present during the time of dinosaurs? The reason for this can be explained through the evolution of plants. Angiosperms started to evolve and became dominant during the Cretaceous period. This is the period where the dinosaurs began to go extinct.

So during the triassic and jurassic period, which kind of plants were abundant? Just think about the plants which we can see around the dinosaurs. What are they? We can mostly see the plants like Pinus, Cycas etc. right? These plants are included in the group called gymnosperms, which were dominant in the Triassic and Jurassic periods.

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Fig: Dinosaurs and their habitat

So now it's clear that angiosperms evolved after gymnosperms and because of this there will be many similarities and dissimilarities between these two plant groups. In this article we are going to discuss more about the differences between gymnosperms and angiosperms.

Table of contents

Gymnosperms

The simple and primitive seed bearing plants without flowers are called gymnosperms. The Greek word ‘gymnos’ means naked and ‘sperma’ means seed. Hence gymnosperms are naked seed bearing plants. Their ovules are naked and their seeds are not enclosed in the ovary. So they are often described as phanerogams without ovaries. They are the most ancient group of seed bearing plants and they emerged during the Palaeozoic era. Around 70 genera and 900 species of gymnosperms are distributed in the tropical and temperate regions.

Fig: Gymnosperms

General characters of gymnosperms

Some of the major general characteristics of gymnosperms are as follows:

  • Most gymnosperms are evergreen trees or shrubs with xerophytic adaptations.
  • They have a sporophytic plant body which is differentiated into roots, stems and leaves.
  • They have a tap root system.

Fig: Tap root of Pinus

  • Some plants have roots which show symbiotic relationship with algae (coralloid roots of Cycas) or fungi (mycorrhizal roots of Pinus).

Fig: Symbiotic relationship in gymnosperm roots

  • Their stem is erect, profusely branched and woody. Two exceptions are the Cycas with unbranched stem and Zamia with tuberous stem.

Fig: Types of stems in gymnosperms

  • An important feature of gymnosperms is the presence of leaf scar (mark left by the leaves after it falls off) in the stem.
  • They have dimorphic leaves. Two types of leaves can be observed and they are foliage leaves and scale leaves.
  • Foliage leaves are green, simple, needle shaped or pinnately compound.
  • Scale leaves are minute and deciduous.
  • Roots show diarch to polyarch condition.
  • Young stem has a ring of open and collateral vascular bundles.
  • Xylem components include tracheids, xylem fibres and xylem parenchyma; but vessels are absent (exception is shown by Gnetum with xylem vessels).
  • Phloem components are sieve cells, albuminous cells, phloem fibres and phloem parenchyma; companion cells are absent.
  • Stem shows distinct secondary growth with conspicuous annual rings in the wood.
  • Leaves of gymnosperms have thick cuticles and sunken stomata.
  • Mesophyll tissues can be differentiated into palisade and spongy tissues or undifferentiated.
  • Differentiated mesophyll tissues are seen in Cycas and undifferentiated mesophyll tissues are seen in Pinus and Cedrus.
  • Lateral translocation of materials is taking place with the help of transfusion tissue, because most of the leaves do not have lateral veins.
  • Megasporangia in megasporophyll and microsporangia in microsporophyll are seen, hence gymnosperms are heterosporous.
  • Cones or strobili are formed by the fusion of sporophylls.
  • Cones are unisexual or monosporogenic. Exception is seen in Ephedra, which has bisporangiate cones.
  • The lifespan of male cones is very less, but female cones are persistent on the plant for a long time.

Fig: Male and female cone

  • Based on the presence of strobili or cone in the gymnosperms, there are two types of sporophytes. They are bisexual gymnosperms having both male and female strobili (monoecious) and unisexual gymnosperms having either male or female strobili (dioecious).

Fig: Monoecious and dioecious gymnosperms

  • Ovules or megasporangia are naked.
  • There are three layers present in the ovular integument and they include a fleshy outer and inner layer and a stony middle layer.
  • The liberation of microspores occurs at the 3 celled stage in Cycas, 4 celled stage in Pinus and 5 celled stage in Ephedra.
  • Gymnosperms have non-motile male gametes. Exceptions to this are the motile male gametes of Ginkgo and Cycas.
  • The number of archegonia in a female gametophyte may vary. The structure of archegonia has a single egg and a veneer canal cell. Neck canal cells are absent.
  • The pollination in gymnosperms usually occurs through wind or by anemophily.
  • Embryonic development takes place before fertilisation, hence endosperm is haploid.
  • The naked ovule develops into seed and the ovular integuments form the seed coat.
  • The number of cotyledons in a seed is one, two or many.
  • Secondary growth can be observed in gymnosperms.
  • There is a distinct alternation between sporophytic and gametophytic generations.
  • They have a diplontic life cycle with dominant diploid sporophytic phase.

Fig: Life cycle of gymnosperms

Classification and examples of gymnosperms

Gymnosperms can be classified into four classes and they are as follows along with their examples:

  • Cycadophyta - Cycas, Zamia, Williamsonia and Lepidopteris.

Fig: Cycadophyta

  • Ginkgophyta - Ginkgo and Trichopitys.

Fig: Ginkgo

  • Coniferophyta - Pinus, Cedrus and Cupressus.

Fig: Coniferophyta

  • Gnetophyta - Gnetum, Ephedra and Welwitschia.

Fig: Gnetum

Angiosperms

The seed bearing plants with the flowers are called angiosperms. The Greek word ‘angion’ means vessel and ‘sperma’ means seeds. Hence the angiosperms are the plants in which the seeds are covered by fruits. In them the pollen grains and ovules are developed in specialised structures called flowers. Before fertilisation, the ovules remain enclosed by the ovary. It is the same for the seeds after fertilisation in them. So they are phanerogams with ovaries. Angiosperms are the most advanced group of plants. They emerged during the late Permian period. They are the largest and diverse group of the Plant Kingdom with 300,000 species. 80 percent of all living green plants are included in the angiosperms.

GIF: Blooming of flowers in angiosperm plants

General characters of angiosperms

Some of the major general characteristics of angiosperms are as follows:

  • Angiosperms occur in a wide range of habitats.
  • Their size ranges from tiny or almost microscopic Wolffia to the tall trees like Eucalyptus (over 100 metres).
  • The size of the flower also varies and the smallest one is Wolfia and largest is Rafflesia.

Fig: Smallest and largest flower

  • Angiosperm plant body is mainly divided into three parts; roots, stems and leaves.
  • According to the number of cotyledons present, there are two groups of plants in angiosperms such as dicotyledons and monocotyledons.

GIF: Germination of seeds in dicotyledons and monocotyledons

  • Dicots have two cotyledons while monocots have only one cotyledon.
  • The dicots have a tap root system and the leaves have reticulate venation.
  • Fibrous root system is seen in monocot plants and they have parallel venation in the leaves.
  • Symbiotic association between bacteria and leguminous roots can be observed. Examples include Rhizobium in the roots of pea plants.
  • The plant bears flowers, fruits and seeds at maturity.
  • Vascular tissues like xylem and phloem are present for the conduction in the angiosperms.
  • Xylem is used for the conduction of water and minerals. It is composed of tracheids, xylem fibres, xylem vessels, and xylem parenchyma.
  • Phloem is used for the conduction of food and the major components of phloem are the sieve tubes, companion cells, phloem parenchyma and phloem fibres.
  • Xylem and phloem are arranged in the form of vascular bundles.
  • Angiosperms are seed bearing plants and the seed contains embryos.
  • The seeds are enclosed and protected by the fruit.
  • Flowers are the reproductive part of the angiosperms and they are attractive in most cases.
  • Flowers attract the pollinating agents like insects and the pollination happens through entomophily mainly. Pollination can also happen through wind (anemophily), water (hydrophily), animals (zoophily), bats (chiropterophily), snails (malacophily), ants (myrmecophily) etc.

GIF: Pollination by biotic agents

  • Flowers are the aggregation of sporophylls (specialised leaves) and they are arranged in a short axis called thalamus.
  • There are four whorls of floral leaves and they are calyx, corolla, androecium and gynoecium.
  • Calyx (whorl of sepals) and corolla (whorl of petals) are non reproductive parts of a flower. Calyx is mainly for protection and corolla is for attracting the pollinators. Hence are called the non essential whorls.
  • The male reproductive organ of the flower is called androecium and it is the whorl of stamens or microsporophylls. It possesses pollen grains.

Fig: Different types of pollen grains

  • The female reproductive organ of the flower is called gynoecium and it is the whorl of carpels or pistils or megasporophylls. It possesses a stigma, style and an ovary.
  • Gynoecium and androecium are the essential whorls.
  • Reproductive events in angiosperms can be divided into three types such as pre-fertilisation events, fertilisation events and post-fertilisation events.
  • Fertilisation is the fusion of male and female gamete (egg).
  • Formation of pollen tubes during fertilisation (siphonogamy) is an important event.

GIF: Pollen tube formation

  • Double fertilisation is a unique feature of angiosperms.
  • The fusion of one of the male gamete (n) and the female gamete (n) results in the formation of a diploid zygote (2n) and this is known as syngamy.
  • Zygote gradually develops into the embryo.
  • The other male gamete (n) fuses with a central cell having two polar nuclei (2n) and forms a triploid primary endosperm cell (3n) with primary endosperm nucleus or PEN, which later forms the endosperm. This is known as triple fusion.
  • Endosperm is the nutritive tissue.
  • Syngamy and triple fusion are together called double fertilisation.

GIF: Double fertilisation in angiosperms

  • After fertilisation, the ovary develops into fruits, ovary wall develops into fruit wall or percarp, integuments develop into seed coats and ovule develops into seeds.
  • Secondary growth can be observed in dicot plants, but not in monocots.
  • They have a diplontic life cycle with dominant diploid sporophytic phase.

Fig: Life cycle of angiosperms

Classification and examples of angiosperms

On the basis of the number of cotyledons, angiosperms can be divided into two classes as follows:

Dicotyledonae - Mango tree, Hibiscus, teak, rose etc.

Fig: Dicotyledons

Monocotyledons - Coconut tree, palm, bamboo, sugarcane etc.

Fig: Monocotyledons

Differences between gymnosperms and angiosperms

The major difference between gymnosperms and angiosperms are as follows:

Gymnosperms

Angiosperms

It is the largest and most diverse group in the Plant Kingdom

It is the smaller and more ancient group in the Plant Kingdom

Variety of plant body types present here, ranging from annual herbs and climbing vines to massive trees

Mostly large woody trees and shrubs present in this group. The only gymnosperm genus with climbing vines is the Gnetum.

They possess scale like or needle like leaves

They possess flat leaves

Stem is soft wood type

Stem is hard wood type

Mostly taproot system present

Taproot and fibrous root system are present

Woody sporophylls present in them which aggregates to form cones

Delicate sporophylls present in them aggregate to form flowers

Cones does not have sepals and petals

A flower has sepals and petals

Cones are generally unisexual, bisexual cones are present in Gnetales (Ephedra, Gnetum and Welwitschia)

Flowers can be unisexual or bisexual

Cones have elongated central axis

They have small and disc shaped thalamus

Microsporophylls are broad and not distinguished into filament and anther

Microsporophyll consists of filament and anther

Each microsporophyll has two to many microsporangia

Four microsporangia or pollen sacs are present in each anther

Megasporophyll does not have stigma, style and ovary

Megasporophyll have stigma, style and ovary

Megasporophylls are woody and unrolled

Megasporophylls are delicate and rolled to form flowers

Placenta is absent

Placenta is present

Ovules are exposed on megasporophylls

Ovules are placed inside the ovary

Ovule is covered by a three layered integument

Ovule is covered by one or two thin integuments

Micropyle is wide

Micropyle is small

Pollen grains directly reach the exposed ovules during pollination

Pollen grains reach the stigma during pollination

Pollination is mainly through wind (anemophily)

Pollination can be through wind (anemophily), water (hydrophily), insects (entomophily), animals (zoophily) etc.

Female gametophyte is large and parenchymatous

Female gametophyte is represented by a seven celled eight nucleated embryosac

One pollen fuses with one egg and no double fertilisation present

Double fertilisation takes place here

Endosperm formation occurs before pollination

Endosperm formation occurs after fertilisation

Haploid endosperm present

Triploid endosperm present

Seeds usually formed in unisexual cones, known as strobili

The seeds develop in the ovaries of flowers

Seeds are not protected by a fruit

Seeds are surrounded by a protective fruit

Xylem vessels are absent exception is shown by Gnetum which has vessels

Xylem vessels are present for conduction

Phloem components include sieve cells, albuminous cells, phloem parenchyma, and phloem fibres

Phloem components include sieve tube elements, companion cells, phloem fibres and phloem parenchyma

Examples include Cycas, Zamia, Williamsonia, Lepidopteris, Ginkgo, Trichopitys, Pinus, Abies, Cupressus, Gnetum, Ephedra, Welwitschia etc.

Examples include Mango tree, Hibiscus, teak, roses, Coconut tree, palm, bamboo, sugarcane etc.

Fig: Gymnosperms

Fig: Angiosperms

Practice Problems

1. The major difference between gymnosperms and angiosperms is

  1. having naked ovules
  2. having fruits
  3. having seeds
  4. All the above

Solution: The simple and primitive seed bearing plants without flowers are called gymnosperms. The Greek word ‘gymnos’ means naked and ‘sperma’ means seed. Hence gymnosperms are naked seeded plants. Their ovules are naked and their seeds are not enclosed in the ovary. So they are often described as phanerogams without ovaries. The seed bearing plants with the flowers are called angiosperms. The Greek word ‘angion’ means vessel and ‘sperma’ means seeds. Hence the angiosperms are the plants in which the pollen grains and ovules are developed in specialised structures called flowers. Before fertilisation, the ovules remain enclosed by the ovary. It is the same for the seeds after fertilisation in them. So they are phanerogams with ovaries. Hence the correct option is a.

2. Find out the structure which is not a haploid structure in angiosperms?

  1. Antipodals
  2. Endosperm
  3. Egg
  4. Synergid

Solution: Double fertilisation is a unique feature of angiosperms. The fusion of one of the male gamete (n) and the female gamete or egg (n) results in the formation of zygote (2n). This is known as syngamy. Zygote gradually develops into an embryo. The other male gamete (n) fuses with a central cell having two polar nuclei (2n) and forms a triploid primary endosperm (3n) cell with primary endosperm nucleus or PEN, which later forms the endosperm. This is known as triple fusion. Double fertilisation is the combination of syngamy and triple fusion. Embryo sac is the female gametophyte in angiosperms. It is formed from the haploid megaspore. Hence all the cells inside the embryo sac are haploid and it is a seven celled and eight nucleated structure. It comprises three antipodals (n), two synergids (n), one egg cell (n) and one large central cell with two polar nuclei (n). Hence the correct option is b.

3. Find out the correct statement?

  1. All gymnosperms are homosporous
  2. All gymnosperms are heterosporous
  3. Only few gymnosperms are homosporous and mostly all others are heterosporous
  4. All gymnosperms and all pteridophytes are heterosporous

Solution: Megasporangia in megasporophyll and microsporangia in microsporophyll are seen in gymnosperms. They produce two kinds of spores such as microspores and megaspores respectively and hence gymnosperms are heterosporous. Microspores develop into male gametophytes and megaspores develop into female gametophytes. Only a few pteridophytes show the heterosporous condition, such as Selaginella and Salvinia. Hence the correct option is b.

4. Which of the following plants shows symbiotic association in roots?

  1. Cycas
  2. Pinus
  3. Pisum sativum
  4. All of the above

Solution: The roots of Pinus show fungal association. These roots are called mycorrhiza. Fungi help to absorb water and minerals like phosphorus for the plant and the plant, in turn, provides nourishment. Mutualism or symbiosis is the term for this type of beneficial association. A symbiotic association with blue green algae is shown by the coralloid roots of Cycas. The blue green algae help in nitrogen fixation. Cyanobacteria grow on the Cycas. The leguminous plants such as Pisum sativum share a symbiotic relationship with bacterium Rhizobium leguminosarum. It helps in the fixation of atmospheric nitrogen into nitrates. These nitrates can be absorbed by the roots of the legumes. Hence the correct option is d.

FAQs

1. What are the xerophytic adaptations of the leaflets of Cycas?

Answer: The leaflets in the Cycas are termed as pinnules. Some of the xerophytic adaptations of Cycas leaflets are as follows:

Fig: Leaflets in the Cycas

  • Presence of thick cuticle which prevents excess transpiration.
  • Thick walled parenchyma cells in the epidermis.
  • Hypodermis is sclerenchymatous.
  • Sunken stomata that are distributed only on the lower epidermis.
  • Midrib is unbranched.
  • Presence of transfusion tissue.

2. Why are cycads called living fossils?

Answer: Cycads are the ancient group of tropical plants that can produce cones. Since they have existed for more than 200 million years ago they are called living fossils. This period existed even before the time of dinosaurs. They were abundant during the Triassic and Jurassic periods. They survived the mass extinctions, ice ages, continental drifts and other challenges. But they are in great trouble today.

Fig: Cycas

3. What was the first flower formed?

Answer: The flowers of Archaefructus an extinct genus of herbaceous aquatic seed plants are considered as the first flower. This ancient plant was found in Liaoning, which is a coastal province in Northeast China. The flowers of Archaefructus were small, simple and this plant is considered as one of the first flowering plants. These plants lived around 130 million years ago and they grew in water or near the water.

4. What is the APG system of classification?

Answer: The first version of a modern and molecular based system of plant taxonomy is the APG system or angiosperm phylogeny system of plant classification. It was published in 1998 by the angiosperm phylogeny group. 462 families and 40 orders are recognised by the APG system of classification.

YOUTUBE LINK: https://www.youtube.com/watch?v=xSq5NU5Wn_U

https://www.youtube.com/watch?v=cucmmMpuKZc&t=2895s

 

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