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Evolution and Speciation in Animals

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This book represents the first attempt to quantify environmental factors and life history traits that accelerate or decelerate species diversity in animals. About 15%, 8% and 77% of species are distributed in marine (70% of earth’s surface), freshwater (< 1%) and terrestrial (~ 29%) habitats. Hence, the terra firma fosters more diversity. The harsh hadal, desert and elevated montane habitats restrict diversity to 0.5-4.2%. Costing more time and energy, osmotrophic and suspension modes of food acquisition limit diversity to < 20%. In minor phyletics, evolution has proceeded from a ‘wrong combination’ of low motility and gonochorism to sessility and hermaphroditism. The motile major phyletics are more speciose (166,279 species/phylum) than the latter (1,975 species/phylum). As evolution and speciation are driven by motility, sessility is limited to 2.9% animals.

Selfing hermaphrodites (0.9%), parthenogens (< 0.6%) and clonals (~ 2%) miss meiosis and/or fertilization. Unable to tolerate them together, animals mutually eliminate parthenogenesis and hermaphroditism as well as parthenogenesis and cloning from each other. In clonals, colonial budding (94%) is more common than costlier fragmentation in solitary clonals. The newly proposed hypothesis explains that each stem cell plays an additive role and the required mass of stem cells differs for cloning and regeneration.

Incidence of heterogamety is four-times more in males than in females. Hence, evolution is more a male-driven process. Egg size is determined by environmental factors, but lecithality is genetically fixed. In poikilotherms, sex is also determined by gene(s), but differentiation by environmental factors. The extra-ovarian vitellogenesis (> 96%), spermatozoan (81%) rather than spermatophore mechanism of sperm transfer, promiscuity and polygamy over monogamy, iteroparity (99.6%) over semelparity and internal fertilization (84%) are preferred, as they accelerate diversity. Body size and egg size determine fecundity. Indirect life cycle (82%) and incorporation of feeding larval stages accelerate diversity. Brooding and viviparity (6.4%) decelerate it. Parasitism extends life span and liberates fecundity from eutelism.

Evolution is an ongoing process, and speciation and extinction are its unavoidable by-products. The in-built conservation mechanism of reviving life after a sleeping duration has been reduced from a few million years in microbial spores to a few thousand years in plant seeds and a few hundred years in dormant eggs in animals. Hence, animal conservation requires priority. The existence of temperature-resistant/insensitive individuals, strains and species shall flourish during the ongoing global warming and earth shall continue with such burgeoning species, hopefully inclusive of man.

Author(s): T. J. Pandian
Publisher: CRC Press
Year: 2021

Language: English
Pages: 346
City: Boca Raton

Cover
Title Page
Copyright Page
Preface
Acknowledgements
Table of Contents
1. General Introduction
Introduction
1.1 Morphological and Molecular Taxonomy
1.2 Evolution and Species Diversity
1.3 Life and Species: Their Origin
1.4 Inheritance and Sex
1.5 Phylum vs Species Diversity
1.6 Biodiversity: Species Diversity
Part A: Environmental Factors
2. Spatial Distribution
Introduction
2.1 Habitat Distribution
2.2 Vertical Distribution
2.2.1 Reproduction and Residency
2.2.2 Distribution in the Oceans
2.2.3 Distribution in Freshwaters
2.4 Terrestrial Distribution
3. Coevolution and Diversity
Introduction
3.1 Symbiosis and Diversity
3.2 Escape and Radiate
3.3 Hosts and Parasites
4. Food and Feeding Modes
Introduction
4.1 Food and Reproduction
4.2 Food Acquisition Cost
4.3 Feeding Groups
4.3.1 Fluid Feeders
4.3.2 Fluid Suckers
4.3.3 Suspension Feeders
4.4 Macrophagy
Part B: Life History Traits
B1: Sexuality
5. Gonochorism and Males
Introduction
5.1 Quantification
5.2 The Males
5.2.1 Size Reduction
5.2.2 Ratio Reduction
6. Hermaphroditism and Selfing
Introduction
6.1 Gonadal Diversity
6.2 Inbreeding and Consequences
6.3 Sequential Hermaphroditism (SQH)
6.4 Behavioral Gonochorism
6.5 Meiosis vs Fertilization
7. Parthenogenesis and Unisexualism
Introduction
7.1 Taxonomic Distribution and Quantification
7.2 Unisexualism
8. Clonals and Stem Cells
Introduction
8.1 Taxonomic Distribution
8.2 Solitary vs Colonial
8.3 Larval Cloners
8.4 Stem Cells and Sources
8.5 Regeneration and Clonals
8.6 Clonality and Diversity
B2: Gametogenesis and Fertilization
9. Mitosis and Meiosis
Introduction
9.1 The Beginnings
9.2 Proliferation of PGCs
9.3 Spermatogonium and Oogonium
9.4 Allogenics and Xenogenics
9.5 Minor Phyla
10. Oogenesis and Vitellogenesis
Introduction
10.1 Vitellogenesis
10.2 Patterns of Oogenesis
10.3 Micropyle and Hybridization
11. Spermatogenesis and Spermiogenesis
Introduction
11.1 Sperm Types and Quantification
12. Female- vs Male-Heterogamety
Introduction
12.1 Chromosomal Mechanism
12.2 Taxonomic Distribution
12.3 Survival of Heterogametics
13. Eutelism and Parasitism
Introduction
13.1 Parasitism and Fecundity
13.2 Sperm Limitation and Sterility
14. Monogamy and Polygamy
Introduction
14.1 Taxonomic Survey
14.2 Monogamy
14.3 Polygamy
14.3.1 Polygyny
14.3.2 Polyandry
15. Semelparity vs Iteroparity
Introduction
15.1 Taxonomic Distribution
15.2 Semelparity and Migration
15.3 Escape Routes
15.4 Semelparous Males
16. Spawning and Oviposition
Introduction
16.1 Taxonomic Survey
16.2 Gamete Transfer Routes
16.3 Broadcast Spawners
16.4 Spermatophore and Economy
17. Fertilization Success
Introduction
17.1 Aquatic Habitats
17.2 External Fertilization—Surprises
17.3 Terrestrial Habitats
18. Fecundity
Introduction
18.1 Terms and Definitions
18.2 Fecundity-Body Size
B3: Embryogenesis and Development
19. Direct and Indirect Life Cycles
Introduction
19.1 Taxonomic Larval Distribution
19.2 Quantification
20. Brooding and Viviparity
Introduction
20.1 Taxonomic Survey
20.2 Vivipares: Size and Fecundity
20.3 Brood: Size and Fecundity
21. Feeding and Non-feeding Larvae
Introduction
21.1 Egg size
21.2 Lecithality
21.3 Incubation and Feeding Larvae
21.4 Taxonomic Survey
22. Parasites and Hosts
Introduction
22.1 Parasites: Location Sites
22.2 Taxonomic Survey
23. Sex Determination and Differentiation
Introduction
23.1 Genes and Chromosomes
23.2 Sexualization and Endocrines
23.3 Surgical and Social Induction
24. Metamorphosis and Recruitment
Introduction
24.1 Metamorphosis
24.2 Settlement
24.3 Recruitment
Part C: Past, Present and Future
25. Message from Fossils
Introduction
25.1 Geological Time Table
25.2 Extinction: Examples
25.3 Extinction and Its Causes
26. Conservation
Introduction
26.1 Diapause: Survival Strategy
26.2 Conservation Strategy
26.3 Sleeping Strategy
26.4 Scientific Development
27. Climate Change
Introduction
27.1 Air-Water Interaction
27.2 Aquatic Animals
27.3 Terrestrial Crops and Animals
27.4 Green Shoots and New Hopes
28. References
Author Index
Species Index
Subject Index
Author’s Biography