Angiosperms
Angiosperms are flowering plants that produce seeds enclosed within a fruit. They are the most diverse group of land plants and play a crucial role in ecosystems as food sources for animals and humans. Angiosperms have specialized reproductive structures, such as flowers, which have contributed to their evolutionary success and widespread distribution.
8 Key excerpts on "Angiosperms"
eBook - ePub- Arun K. Pandey, Shruti Kasana(Authors)
- 2021(Publication Date)
- CRC Press(Publisher)
...CHAPTER-19 ORIGIN AND EVOLUTION OF Angiosperms The flowering plants (Angiosperms) constitute the higher group of seed plants with about 3,50,000 species. They are found in far greater range of habitats than any other group of land plants. Angiosperms arose from some unidentified ancestral lineage and diversified rapidly within a short geological time period (Li et al., 2019). To trace the origin of this group has been one of the main emphasis of evolutionary biologist. It has also been popularly called by Charles Darwin as an “abominable mystery”. On July 22, 1879, Charles Darwin famously stated in a letter to Joseph Dalton Hooker that “the rapid development, so far as we can judge, of all the higher plants within recent geological times is an abominable mystery.” Darwin was referring to the apparently abrupt evolutionary origin and subsequent rapid diversification of the Angiosperms (Darwin and Seward, 1903). Angiosperms (from Greek word ‘ angeion’ meaning pot or vessel) are the group of plants in which ovules are formed inside the specialized female reproductive organ known as carpel. They are characterized by the presence of flowers, carpels, columellate pollen, non-motile sperm, elongated pollen tubes with callose plugs, double fertilization leading to endosperm production, highly reduced megagametophytes and microgametophytes, an outer integument enclosing the ovule, paracytic stomata, and vessels in the secondary xylem (Doyle, 2008). Due to these characters, the Angiosperms rapidly radiated into several, distinct lineages and gradually replaced gymnosperms as the dominant plant life form on the earth. In addition to this, the success of the Angiosperms is also attributed to the extensive coevolution with pollinators, herbivores and predators...
eBook - ePubPlant Systematics
An Integrated Approach, Fourth Edition
- Gurcharan Singh(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
...Chapter 9 Phylogeny of Angiosperms Angiosperms form the most dominant group of plants with at least 295,383 (Christenhusz and Byng, 2016), a number much greater than all other groups of plants combined. Not only in numbers, Angiosperms are also found in a far greater range of habitats than any other group of land plants. The phylogeny of Angiosperms has, however, been a much-debated subject, largely because of very poor records of the earliest Angiosperms. These earliest Angiosperms probably lived in habitats that were not best suited for fossilization. Before trying to evaluate the phylogeny, it would be useful to have an understanding of the major terms and concepts concerning phylogeny in general, and with respect to Angiosperms in particular. ORIGIN OF Angiosperms The origin and early evolution of Angiosperms are enigmas that have intrigued botanists for well over a century. They constituted an ‘abominable mystery’ to Darwin. The mystery is slowly being ‘sleuthed’ and at the present pace of ‘Sherlock Holms research’, it may be no more mysterious within the next two decades than for any other major group. With the exception of conifer forest and moss-lichen tundra, Angiosperms dominate all major terrestrial vegetation zones, account for the majority of primary production on land, and exhibit bewildering morphological diversity. Unfortunately, much less is known about the origin and early evolution of Angiosperms, resulting in several different views regarding their ancestors, the earliest forms and course of evolution. The origin of Angiosperms may be conveniently discussed under the following considerations. What are Angiosperms? Angiosperms form a distinct group of seed plants sharing a unique combination of characters. These important characters include carpels enclosing the ovules, pollen grains germinating on the stigma, sieve tubes with companion cells, double fertilization resulting in triploid endosperm, and highly reduced male and female gametophytes...
eBook - ePubThe Jehol Fossils
The Emergence of Feathered Dinosaurs, Beaked Birds and Flowering Plants
- Pei-ji Chen, Yuan Wang, Yuan-qing Wang, Pei-ji Chen, Yuan Wang, Yuan-qing Wang(Authors)
- 2011(Publication Date)
- Academic Press(Publisher)
...Angiosperms Qin Leng, Shun-qing Wu and Else Marie Friis Sinocarpus decussatus Photo: Yvonne Arremo/NRM Angiosperms (flowering plants) are ecologically dominant in most terrestrial vegetation today, accounting for the bulk of the primary productivity on land. They constitute the most species-rich group of land plants that ever existed, with an overwhelming morphological diversity of flowers and growth forms ranging from the tiniest duckweed to the tallest trees, They also occur in most ecosystems on land from deserts to coastal swamps and even have representatives living in the oceans. Despite their prominent position in the modern world, the Angiosperms diversified very late in the history of land plants and their rise to ecological dominance took place over a relatively short time interval during the Cretaceous, more than 300 million years after plants’ first invasion onto the land. The earliest unequivocal angiosperm fossils are pollen grains from Valanginian—Hauterivian strata of Israel (Brenner, 1996) and southern England (Hughes, 1994), about 130~ 135 million years old. Angiosperms are rare in these earliest Cretaceous strata but by the Barremian—Aptian, 10~15 million years after their first occurrence, they were already widely established, and the transition from the ancient Mesozoic vegetation, dominated by gymnosperms (cycads, ginkgos, seed ferns, bennettitaleans, conifers) and pteridophytes (lycopods, horsetails, ferns), to the modern ecosystems was well under way. Plum trees, tea bushes, walnut trees, sunflowers, rice, and the crops that give us our breakfast cereals are among the familiar Angiosperms essential to our everyday lives. The first Angiosperms shared many features with their present-day descendants, but they were also different. How different, we do not fully know...
eBook - ePub- Laurie Ann Callihan(Author)
- 2013(Publication Date)
- Research & Education Association(Publisher)
...CHAPTER 4 Plants (Botany) CHAPTER 4 PLANTS (BOTANY) Most of us commonly recognize plants as organisms that produce their own food through the process of photosynthesis. (Some bacteria are also photosynthetic.) However, the plant kingdom is divided into several classifications according to physical characteristics. Vascular plants (tracheophytes) have tissue organized in such a way as to conduct food and water throughout their structure. These plants include some that produce seeds (such as corn or roses) as well as those that do not produce any seeds (such as ferns). Nonvascular plants (bryophytes), such as mosses, lack specialized tissue for conducting water or food. They produce no seeds or flowers and are generally only a few centimeters in height. Another method of classifying plants is according to their method of reproduction. Angiosperms are plants that produce flowers, which are reproductive organs. Gymnosperms, on the other hand, produce seeds without flowers. These include conifers (cone-bearers) and cycads. Plants that survive only through a single growing season are known as annuals. Other plants are biennial ; their life cycle spans two growing seasons. Perennial plants continue to grow year after year. PLANT ANATOMY Plants have structures that allow them to thrive in their environment. Angiosperms and gymnosperms differ mostly in the structure of their stems and reproductive organs. Gymnosperms are mostly trees and shrubs, with woody, instead of herbaceous stems. Gymnosperms do not produce flowers; instead they produce seeds in cones or cone-like structures. Fig. 4-1 A Typical Flowering Plant (angiosperm). Note descriptions of numbered structures in text. Angiosperms The shoot system of Angiosperms includes the stem, leaves, flowers, and fruit, as well as growth structures such as nodes and buds (see Fig. 4-1). The signature structure of an angiosperm is the flower (1), the primary reproductive organ...
eBook - ePubPhylogeny and Evolution of the Angiosperms
Revised and Updated Edition
- Douglas Soltis, Pamela Soltis, Peter Endress, Mark W. Chase, Steven Manchester, Walter Judd, Lucas Majure, Evgeny Mavrodiev(Authors)
- 2018(Publication Date)
- University of Chicago Press(Publisher)
...A topic of particular intrigue has been the closest relatives of the Angiosperms. Angiosperms are responsible either directly or indirectly for the majority of human food and account for a huge proportion of photosynthesis and carbon sequestration. They have diversified to include 350,000–400,000 species in perhaps 130–170 myr and now occur in nearly all habitable terrestrial environments and many aquatic habitats. Understanding how Angiosperms accomplished this is of fundamental evolutionary and ecological importance. At some point, nearly every living and fossil group of gymnosperms has been proposed as a possible ancestor of the Angiosperms (e.g., Wieland 1918; Thomas 1934, 1936; Melville 1962, 1969; Stebbins 1974; Meeuse 1975; Long 1977; Doyle 1978, 1998a,b; Retallack and Dilcher 1981; Crane 1985; Cronquist 1988; Crane et al. 1995; reviewed in Doyle 2006, 2008, 2012; Friis et al. 2011). Among extant seed plants, the relationship between Angiosperms and Gnetales has received considerable attention. Ascertaining the closest relatives of the Angiosperms is not only of great systematic importance but also critical for assessing character evolution. For example, the outcome of investigations of character evolution among basal Angiosperms, including studies focused on the origin and diversification of crucial angiosperm structures (e.g., floral organs, endosperm, vessel elements), may be influenced by those taxa considered their closest relatives. The effect of outgroup choice on the reconstruction of character evolution within Angiosperms is readily seen via the widespread use of Gnetales as an outgroup for Angiosperms. As reviewed below, for nearly two decades beginning in the 1980s, Gnetales were considered by many to represent the closest living relatives of the Angiosperms...
eBook - ePubCrop Pollination by Bees, Volume 1
Evolution, Ecology, Conservation, and Management
- Keith Delaplane(Author)
- 2021(Publication Date)
- CAB International(Publisher)
...Make no mistake, flowering was a wildly successful innovation. Angiosperms today are among the most successful of all life forms. They comprise up to 400,000 named species, making up nearly 90% of all terrestrial plants (Jarvis and Linné, 2007). They embrace virtually every known plant body form and growth strategy and occupy every terrestrial habitat on Earth (Crepet and Niklas, 2009). The flower was certainly front and centre of these developments, so let us think a moment about the innovations a flower does, and does not, represent. To begin, flowers do not mark the beginning of pollen or ovules; these were already here millions of years earlier, entering the fossil record together (not uncoincidentally) in the late Devonian around 365 million years ago (mya) (Fairon-Demaret, 1996 ; Wang et al., 2016), fully double the antiquity of the flowers (183 mya; Fig. 1.1). Pollen and ovules are rather the common legacy of all seed plants – the group that includes the Angiosperms and the gymnosperms. Neither do flowers signal the beginning of insect pollination. Evidence for that comes from as early as 320–300 mya (Crepet, 1979), predictably after the arrival of ovules and pollen but long before the Angiosperms. Flowers do not mark the beginning of nectar. The pollination drop described in the previous section is living evidence for the kinds of pre-angiosperm ovule secretions that evolution would later coopt into sugar rewards for flower visitors...
eBook - ePub- Andrew Lack(Author)
- 2022(Publication Date)
- Garland Science(Publisher)
...4 REPRODUCTION DOI: 10.1201/9781003104711-4 In this chapter, we will consider sexual reproduction in all its forms in plants. Asexual reproduction and vegetative growth are considered in Chapter 3. The different groups of plants reproduce in different ways, and all the main part is concerned with flowering plants. Bryophytes and ferns are considered briefly at the end of the chapter. Among seed plants, pollen is produced that must reach the ovules. To reach the ovules of another individual, plants inevitably rely on an external factor. Wind, insects, birds and bats are the main pollinators, though water, non-flying mammals and, occasionally, other animals are important for a few plants. An estimated 87 per cent of all flowering plant species are pollinated by animals, although the proportion is nearer 70 per cent in temperate communities and over 90 per cent in wet tropical forests, and communities differ widely. Wind-pollination accounts for most of the rest, but this underestimates its importance, as the common dominant trees in temperate communities are nearly all wind-pollinated, as are grasses the world over (with the exception of a handful of rainforest grasses that attract insects). Water pollination is rare even for aquatic plants, though the so-called “sea-grasses” and a few submerged freshwater plants are pollinated by water. Something over 80 per cent of all species of flowering plants are hermaphrodite, with each flower bearing fertile stamens, producing pollen, and carpels with ovules. Some 7 per cent of flowering plants are dioecious, like most animals, with staminate (male) flowers on separate plants from those bearing flowers with only car pels. About 5 per cent of flowering plants are monoecious, i.e. plants with unisexual flowers but both types of flower borne on the same plant...
- Ian Clarke, Helen Lee(Authors)
- 2019(Publication Date)
- Melbourne University Press Digital(Publisher)
...4 Reproduction Reproduction in Flowering Plants may be either sexual or asexual. Sexual reproduction involves the fusion of male and female reproductive cells known as gametes. In asexual reproduction no fusion of gametes takes place and the reproductive entities are vegetative bodies such as corms, tubers, bulbs, cuttings etc. Sexual reproduction may be dealt with in a number of stages: • pollination—the transfer of pollen from anthers to stigma • fertilisation—union of male and female gametes • development of the seed • development of the fruit • germination of the seed. Pollination The transfer of pollen, which carries the male gamete, to the stigma takes place in several ways. Many plants are pollinated by wind including the conifers (pines and their allies), she-oaks and grasses, and many northern hemisphere trees such as birches, alders and oaks. These plants produce large quantities of pollen and release it into the air, and it may float or be blown onto a compatible stigma. The stigmas of wind-pollinated plants are commonly large and feathery, which gives them a better chance of trapping pollen. Insects are the most important pollinators of flowers. They visit to collect nectar or pollen or both, and at the same time incidentally transfer some pollen from one flower to another. Insects locate flowers by odour and then are influenced by colour and shape. It is known that bees preferentially visit yellow or blue flowers whereas moths, which emerge in the evening, are attracted to white or cream flowers, which are more readily seen at that time. Birds, particularly honeyeaters, are important pollinators of flowers with tubular corollas, to which they are attracted by the presence of copious nectar. Pollen catches on the head feathers of the birds as they probe for nectar and then is carried to other flowers. Birds seem to be attracted to red flowers, but they visit other colours if nectar is available...
