Evolution Overview & Human Placing in Nature

L1 Overview: Evolution & Placing Human in Nature

• Sophisticated knowledge of biophysical environments isn't restricted to science.

• Homo sapiens lived as hunter-gatherers.

• Aristotle believed populations remained stable except for occasional plagues; nature maintained a balance.

• Aristotle ordered organisms in a linear sequence, humans at the top.

• Christians believed species were created by an intelligent designer, and the world is eternal and unchanging.

• Archbishop James Ussher (1650) proposed a young Earth.

• George Louis Leclerc Comte de Buffon was a father of evolution and natural history, and questioned the young Earth idea.

• Georges Cuvier noted fossils resembled modern species but many past species were extinct.

• Mary Anning discovered extinct marine reptiles.

• Thomas Malthus's idea of exponential population growth vs. arithmetic growth of resources suggested instability in nature.

• The Diluvial Theory / Catastrophism: fossils represent animals that perished in the biblical flood.

• James Hutton's Uniformitarianism proposed the Earth's landscapes were formed by the same natural processes acting slowly over a long time.

• The Earth is very, very old.

L2 The Scientific Approach 1: How do ecologists investigate problems?

• Science involves investigating and asking questions about the world.

• Key historical methods: observational astronomy (Galileo), rationalism (Descartes), reductionism, empiricism (Bacon).

• Hypothesis testing is essential in science, needing repeatable experiments.

• Proximate causes explain how something works, while ultimate causes explain why.

• Four main types of ecological investigation: description and observation, hypotheses, predictions, and experimental testing.

• Management involves applying understanding to influence original patterns.

• Proper experimental design, including appropriate sample size and accounting for confounding variables, are crucial for repeatable and trustworthy results.

L3 The Scientific Approach 2: Doing Ecological Experiments

• Setting up null and alternative hypotheses.
• Importance of sampling methods, including systematic and random sampling.
• The 'rules of 10' (e.g., 10 replicates for each variable) in sampling.
• Alpha and beta diversity.
• Methods to determine competition: comparisons of species distributions, identifying common species, demonstrating resource limitations, and manipulating population sizes.
• Bias in ecological research – positive results, novelty, are more likely to be published than negative ones; taxonomy biases exist.
• Important to consider the generality and limitations of experimental results.
• Considerations for good experimental design: matching the questions to the scope of the research, ensuring samples are large enough and replication thorough, and appropriately interpreting the results.

L4 The Scientific Approach 3: How do we deal with environmental complexity?

• Experiments for investigating ecological problems: mensurative, observational; manipulative, formal procedure.

• Manipulative experiments compare treatments with a control group.

• Types of experiments include laboratory (LE), field (FE), and natural experiments (NE).

• Factors influencing the choice of experiments: control of variables, scope and scale, number of species, ease, and cost.

• Dealing with environmental complexity, especially conflicting explanations.

• Strong inference methods.

• Proper experiment design and replication essential for trustworthy conclusions.

L5 What is evolution by natural selection?

• Evolution is the accumulation of changes in organisms' characteristics over generations.
• Darwin's theory of evolution by natural selection hinges on variation, heredity, and limited resources leading to competition; individuals with advantageous traits have more offspring.
• Necessary conditions: variation, heritability, influence of the environment on survival and reproduction.
• Time available for evolution: Earth's age, earliest fossils, and the evolution of Homo sapiens.
• Macroevolution: large-scale changes over a long time, including speciation.
• Types of Speciation: allopatric, peripatric, parapatric, sympatric.

L6 What are the ecological outcomes of natural selection?

• Evolution is a 2-stage process involving mutation, which creates variation; natural selection determines which variations are passed to future generations.
• Fitness is the relative contribution an individual makes to future generations.
• Adaptive strategies can be: directional, stabilizing, disruptive.
• Sexual Selection: competition between individuals (typically males) for mates, leading to traits that attract mates.
• Inclusive fitness: individual's total evolutionary success considering both direct reproduction and the impact on reproduction of close relatives.

L7 What is biodiversity & why is it important?

• Biodiversity refers to biological diversity - variety of life.

• Often measured at the species level.

• Anthropocene epoch includes factors of habitat degradation, biological invasions, pollution, overexploitation that lead to biodiversity decline.

• Science tries to understand biodiversity and its effects.

• Patterns differ across latitudes, among habitats & ecological levels, within and among taxa, also across habitats and ecosystems.

• Species richness may vary significantly in different ecosystems.

• Global decline of biodiversity.

L8 How do adaptations evolve?

• Genes code for phenotypes, which interact with the environment to influence the survival and reproduction of individuals.

• Natural selection acts on individuals (phenotypes), but genes are selected because of the effect on the phenotype; Genes and phenotypic expression directly link and are influenced by environmental interactions.

• Fitness is the proportionate contribution of an individual to future generations and is directly linked to adaptation.

• Adaptation is any feature helping an organism survive and reproduce in its environment.

• Adaptations can be classified as structural, behavioral, or physiological.

• Examples are given of each type of adaptation.

L9 Species Interaction

• In community ecology, species interact, forming food webs.

• Trophic level describes an organism's position in a food web.

• Ecological role is a species functional role in an ecosystem.

• Niche describes conditions needed for species existence and the role it plays.

• Fundamental niche represents possible environment, while realized niche is the actual environment.

• "Pyramid of numbers" depicts relative numbers of individuals in each trophic level; “Pyramid of Biomass” depicts the biomass; “Pyramid of Energy” depicts energy flow.

• Predation involves predator consuming prey.

• Herbivory involves an organism consuming plants or plant parts, usually not resulting in plant death.

• Parasitism involves one species (parasite) consuming part of the host, which may or may not result in host death.

• Competition occurs when two species require the same resources, leading to fitness reduction for one or both species.

• Exploitation competition: competitors share resources.

• Interference competition: species restrict access through direct interaction.

• Species can exploit resources differently – "resource partitioning."

• Mutualism, commensalism.

L10 The mating game: conflict or cooperation between the sexes?

• Monogamy: relationship where one male and one female form a pair bond.

• Polygamy: male or female has more than one mate; Polygyny: one male with many females Polyandry: one female with many males

• Reproductive success in animals often relies on the number and quality of mates.

• Female reproductive success often is limited by resources, while males often are limited by access to females (mate availability).

• Implications of varying sex ratios are discussed, and their relation to variation in population fitness.

• Consequences of differing sex ratios, including the Trivers-Willard effect, local mate competition, and resource enhancement, are analyzed.

L11 Is insect colouration a defensive adaptation?

• The life-dinner principle describes the selective pressure on prey (escape) and predator to maximize their fitness (consume more prey or survive longer).

• Two common approaches for predator-prey coexistence: top-down (predators controlling prey numbers) and bottom-up (resources controlling prey population numbers).

• Protective adaptations are against physical, chemical, and other dangerous factors, and typically involve traits that help species survive in their environment.

• Defensive adaptations describe the ways organisms protect themselves from attacks by other organisms (usually predators).

• Protective strategies include crypsis (camouflage) and aposematism (bright colors warning of noxiousness).

• Coevolution, coevolutionary interactions are described between predator and prey.

• Defensive arsenal of prey – crypsis, mimicry, and aposematism.

L12 Optimal foraging: What to eat, where, when and how?

• Foraging: Exploitation of resources; often referring to food resources.

• Foraging Modes: sit-and-wait (ambush), active.

• Determining optimal foraging strategies: factors to consider: spatial/temporal patterns in resource availability, quality of different resources (net energy gain), and cost of obtaining those resources.

• Optimal Foraging Theory explains that organisms should make the most efficient use of their time foraging.

• Foragers should maximize energy gain per unit of time; the costs of getting a resource need to be considered.

L13 What prevents populations from growing indefinitely?

• Populations consist of members of the same species and share environment and resources.

• Limits to population growth are influenced by both intrinsic factors (those internal to a population, such as competition and density-dependent mortality) as well as extrinsic ones (external to a population, such as climate change & catastrophes).

• Density-independent factors (DIF): influence mortality without dependence on population density; factors like climate change and catastrophes affect all members equally.

• Density-dependent factors (DDF): influence mortality with dependence on population density.

L14 Why do some animals live in groups?

• Animals live in groups for various reasons from safety and survival, to mate selection and breeding success.

• In addition to benefits such as safety and resource increase, there is also competition involved in group living.

• Natural selection shapes behaviours that benefit the donor, in conjunction with other factors such as competition & resource availability.

• Groups are often safer from predation due to the dilution effect.

• Groups also facilitate cooperative behaviours like cooperative hunting.

L15 Brilliant bats, and examples of co-evolution

• Predators and prey, in this case bats and moths, are in a constant selection pressure to adapt to survive their relationships.

• Sensory adaptations (hearing and echolocation in bats, tympanic ears for hearing ultrasound in moths).

• Behavioral strategies for predator avoidance (escape, distraction, confusing the predator), some insects have evolved ultrasound generating abilities, like some moths.

• Co-evolution: moths have developed defenses like camouflage, and aposematism against predation by bats, and both parties have evolved to adapt to environmental changes; Some insects can mimic their environment effectively or adopt visual, audial, thermal cues of color or physical attributes to gain protection from predators.

L16 The Evolution of sex ratios

• Anisogamy involves the production of gametes of different sizes (typically eggs are large and sperm are small); this difference in gamete size influences the sex ratio evolutionarily.

• Females are often ‘limiting resource’ for males in relation to mating.

• Fisher's principle suggest that a population with a 1:1 sex ratio will be more successful than one with a skewed sex ratio.

• Implications of sex allocation, and its importance for species' fitness, are described, with examples.

L17 Case study 2: How (or why) did the guppy get its spots?

• Guppies (Poecilia reticulata) show great diversity in colour and spot patterns; variation in colours may occur due to environmental conditions or predation, particularly in low-risk environments.

• Live-bearing, giving rise to significant reproductive potential and populations fluctuating in size rapidly.

• Guppies show an example of natural selection and sexual selection interacting (to respond to predation and attract mates).

• Endler's experiments (controlled pool experiments and field transplants) confirmed that natural selection can strongly influence species adaptation (traits), depending on environmental conditions.

L18 Human Evolution: where did we come from?

• Primates have 2 suborders: Prosimii & Anthropoidea.

• Key primate characteristics: heterodont dentition (differentiated teeth), presence of five digits, and grasping hands (flexible).

• Primates' adaptations for life in trees (arboreal life) are discussed.

• Evolutionary history of primates, including humans, is complex and nonlinear.

• Hominins evolved and diversified over millions of years; fossil evidence suggests an important role for bipedalism (walking on two legs).

• Some key species like Australopithecus are discussed; characteristics, adaptations, and environment is presented.

• Homo species, including Homo habilis, Homo erectus, to Homo Neanderthalensis and Homo sapiens are highlighted as crucial evolutionary steps.

L19 Human Evolution: Meet the relatives

• Scarcity of fossils makes it difficult to decipher human evolution completely, including complications of age ranges.
• The Piltdown Forgery is an example of a human evolution hoax.
• Various proposed human evolutionary relatives and characteristics of each are highlighted.

L20 Anthropocene

• The evolution of humans is discussed, along with characteristics such as larger brains and the development of language.

• This chapter investigates the possible factors that may lead to the evolution of larger brains for humans, including ecological challenges of food-finding and social or ecological pressures.

• Cultural evolution, the transmission of knowledge and behaviours across generations, is a hallmark of humans.

• The debate around anthropocene and its importance and causes in relation to species extinction and climate change are covered.

L21

• Global increase in environmental temperatures and its negative impacts on several environmental aspects.

This quiz covers key concepts in the evolution of Homo sapiens and their place in nature, exploring historical perspectives from Aristotle to Malthus. It examines ideas on population stability, extinction, and the interplay between species and their environments. Test your knowledge on these fundamental theories and figures in biology and natural history.