This chapter discusses the presence or absence of sex chromosomes that determines the sex of the individual. It explains that sex is defined by having two different sex chromosomes or being heterogametic, such as human males that are XY. It also looks at the consequences for the inheritance of genes on the X chromosome, wherein different patterns of inheritance are observed for X-linked traits in males and females. The chapter reviews the non-disjunction of the sex chromosomes or the failure to segregate normally during meiosis that results in individuals with unusual numbers of X or Y chromosomes, illuminating some of the different modes of sex determination in some species. It defines sexual dimorphism, wherein different species exhibit physical differences between the sexes in anatomy, physiology, coloration, and behaviour.
Chapter
X-linked Genes and Sex Chromosomes
Chapter
Behavioural ecology
This chapter looks into behavioural ecology. Sexual selection, which is a form of natural selection, helps explain the distinct sexual dimorphism in the secondary sexual characteristics between the sexes alongside kin selection. The chapter recognizes five basic types of animal mating systems: monogamy, polygyny, polyandry, polygynandry, and promiscuity. It notes how molecular techniques have been used to examine dispersal behaviour and enabled dietary analysis. The chapter highlights behaviour playing as a key part in reproductive success in terms of speciation. It mentions how epigenetic modifications of the genome and transgenerational epigenetic inheritance influenced modifications in animal behaviour.
