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Many organisms undergo ontogeny, whereby individuals change in state (e.g., in size, morphology, or condition) as they age. Understanding the evolution of traits influencing ontogeny is challenging because their fitness effects unfold across an individual’s lifetime and may differ between classes such as sexes. Here, we analyse selection on non-plastic traits (e.g., fixed resource allocation strategies) that determine the development of dynamical states throughout life (e.g., body size), with consequences for fecundity and survival in age- and class-structured populations. Using invasion analysis, we derive expressions for directional and disruptive selection that decompose into age- and class-specific components. This allows us to identify convergence stable trait values, assess whether they are uninvadable or potentially experience evolutionary branching, and pinpoint the age and class pathways through which correlational and disruptive selection act. Applying our results to a model of growth under size-mediated sexual selection, we show how selection on growth rates distributes across ages and sexes, and how its relative strength depends on genetic correlations, individual ploidy and life-history. We also show how sex-specific developmental trade-offs and constraints can generate disruptive selection on male growth and favour the evolution of alternative male life histories. More broadly, our results highlight how adaptation is mediated by the interaction of development and demography, and provide tools to investigate how conflicts across ages and classes may influence senescence, sexual dimorphism, and the diversification of ontogenetic strategies.诸多生物都会经历个体发育（ontogeny）过程，即个体随衰老在状态（如体型、形态或生理状况）上发生改变。解析影响个体发育的性状的演化机制颇具挑战，因为这类性状的适合度效应会贯穿个体一生，且在不同类群（如不同性别）间存在差异。本研究针对非可塑性性状（non-plastic traits，如固定资源分配策略）展开选择分析——这类性状决定了个体一生的动态状态（如体型）发育，并会对年龄与类群结构化种群的繁殖力和存活产生影响。借助入侵分析（invasion analysis），我们推导出定向选择与分裂选择的表达式，并将其分解为年龄特异性与类群特异性两部分。借此，我们得以识别收敛稳定的性状值，评估其是否具备不可入侵性，或是否可能发生进化分支，并精准定位相关选择与分裂选择作用的年龄与类群通路。我们将研究结果应用于体型介导性选择下的生长模型，阐明了生长速率相关选择如何在不同年龄与性别间分布，以及其相对强度如何受遗传相关性、个体倍性与生活史的调控。此外，我们还揭示了性别特异性发育权衡与约束如何对雄性生长产生分裂选择，并推动雄性替代生活史的演化。从更广泛的视角来看，本研究结果凸显了适应如何通过发育与种群统计学的相互作用得以调控，并为解析年龄与类群间的冲突如何影响衰老、性二态性以及个体发育策略的多样化提供了研究工具。