Ecologia - Aula 05 - Interações biológicas e evolução

Biological Interactions and Evolution

Overview of Biological Interactions

• The study focuses on biological interactions among living organisms and their environment, emphasizing the complexity of these relationships.

• Interactions can involve one or multiple species, often aiming to optimize resource acquisition for survival.

• Significant interactions impact population dynamics; random encounters do not constitute biological interactions.

• These interactions serve as density-dependent regulatory factors that influence evolutionary processes.

Types of Biological Interactions

Intra-specific vs. Inter-specific

• Biological interactions can be intra-specific (within the same species) or inter-specific (between different species).

• They can also be classified as harmonious (positive effects) or disharmonious (negative effects).

Examples of Harmonious Interactions

Colonies and Societies

• Colonies consist of individuals formed through asexual reproduction, leading to physical continuity, such as coral colonies.

• Societies involve sexual reproduction with distinct roles among individuals, like bees and ants, showcasing division of labor.

Competition and Cannibalism

Intra-specific Competition

• Intra-specific competition occurs when individuals compete for limited resources, potentially harming overall population viability but may enhance genetic fitness over time.

Cannibalism

• Some species exhibit cannibalistic behavior where adults consume younger members for nutritional benefits during reproductive phases.

Negative Interactions: Predation and Competition

Types of Negative Interactions

• Three main types include predation (one species benefits at the expense of another), competition (both are harmed), and parasitism (one is harmed while the other is unaffected).

Predation Dynamics

Direct Predators

• Direct predators kill their prey for sustenance; examples include bears eating salmon or snakes consuming frogs.

Herbivory

• Herbivory is included in predation when plants are consumed by herbivores, impacting plant populations significantly.

Partially Consuming Species

• Some animals engage in partial consumption; mosquitoes feed on blood without killing their hosts immediately.

Understanding Parasitism and Its Interactions

Types of Parasites

• The relationship between parasites and their hosts is intimate and long-lasting, with parasites either attaching to the host's body surface (ectoparasites) or living inside the host (endoparasites).

• Examples include mites that parasitize plants and tapeworms that live in human bodies. Some plants also act as parasites on other plants, such as mistletoe.

• A specific type of parasite called facultative parasites can perform photosynthesis but will develop roots within another plant's tissues when they attach to it.

Parasitic Relationships

• Parasitioids are a unique category where female wasps lay eggs in immobilized prey; the larvae consume the host from within, leading to its death.

• This form of parasitism exemplifies a predation-like interaction where resources become detrimental for the host.

Mathematical Modeling of Interactions

• Interactions between predator and prey populations can be modeled mathematically, estimating their abundance over time based on initial population sizes.

• As prey populations increase due to low predator numbers, predators subsequently grow in number until they exert pressure on prey populations, causing declines.

Population Dynamics

• The cyclical nature of predator-prey relationships is illustrated through real-world examples like hares and lynxes near the Arctic, showing peaks in their populations with delays between them.

• These cycles demonstrate how external factors influence population dynamics beyond just predation.

Evolutionary Implications

• Natural selection plays a crucial role in shaping adaptations among both predators and prey; effective hunting strategies evolve alongside defensive mechanisms.

• Predators like sharks have specialized structures for capturing large prey, while owls possess silent flight adaptations for stealthy attacks.

Defensive Adaptations in Prey

• Prey species exhibit various morphological adaptations for defense against predators, including spines similar to those found on cacti.

Understanding Animal Defense Mechanisms

Coloration and Camouflage in Nature

• Predators can recognize less suitable prey from a distance, often avoiding attacks on brightly colored animals that may indicate toxicity.

• The difficulty of spotting a lizard in an image illustrates the concept of camouflage, similar to the historical example of light and dark moths in England.

• Many animals use coloration for intimidation; for instance, a red surface on a lizard can deter predators by making it appear larger.

• Disruptive coloration helps break up an animal's outline, making it harder for predators to identify them against their environment (e.g., jaguars hiding among foliage).

• Zebras' stripes create confusion for predators by blending individuals together, complicating identification during hunts.

Mimicry as a Defense Strategy

• Mimicry involves harmless species imitating dangerous ones to avoid predation; for example, certain caterpillars resemble snakes to deter birds.

• This strategy protects vulnerable species by creating fear or hesitation in potential predators.

Inter-specific Competition Dynamics

Types of Competition

• Inter-specific competition occurs between different species and can manifest as either exploitation or interference competition.

• Exploitation competition involves indirect resource consumption without direct interaction between species, leading to resource scarcity over time.

Case Study: Resource Availability

• An experiment from 1917 demonstrated how two plant species compete differently based on soil type; one thrives in acidic conditions while the other prefers alkaline soils.

• When both species are present in the same environment (acidic soil), their populations decline due to increased competition, highlighting asymmetrical competitive advantages.

Examples of Interference Competition

Aggressive Encounters

• A scenario where a carnivorous predator encounters another predator with prey exemplifies interference competition through aggressive behavior over resources.

Plant Competition

• Sage plants inhibit competitors by releasing toxic substances into the soil, effectively monopolizing resources and reducing biodiversity around them.

Competitive Exclusion Principle

Understanding Competitive Exclusion and Coexistence

Competitive Dynamics Between Species

• The population growth of Para messi caldato initially outpaces that of Para messi uma orelha, but eventually declines, illustrating competitive dynamics when two species are placed in the same environment.

• In contrast, Para messi uma orelha stabilizes at a higher population level than it would alone, demonstrating a classic example of competitive exclusion where one species can dominate resources.

• When both species coexist in the same culture medium, their populations stabilize at lower abundances compared to when they exist separately, indicating resource competition.

• Despite coexistence, the overall population density is reduced, highlighting how interspecies competition affects individual abundance.

Niche Differentiation and Coexistence

• The phenomenon known as niche displacement allows for coexistence; for instance, two types of Eudragia exhibit similar body sizes but utilize different particle sizes for feeding when in mixed populations.

• In isolated conditions (allopatry), both species consume the same resources leading to niche overlap and competition.

• However, in environments where both species are present (sympatry), larger individuals of one species adapt by consuming larger food particles, reducing direct competition.

Positive Interactions: Mutualism and Commensalism

Types of Mutualism

• Positive interspecific interactions include mutualism—where both species benefit—and commensalism—where only one benefits without harming the other.

Dispersive Mutualism

• An example includes animals aiding in pollination or seed dispersal; bees and hummingbirds serve as key pollinators while ants help disperse seeds.

Defensive Mutualism

• This form involves organisms providing protection; crustaceans cleaning parasites off fish exemplify this relationship.

Trophic Mutualism

• A classic case is mycorrhizal associations between fungi and plant roots where fungi enhance nutrient uptake for plants while receiving carbohydrates in return.

Ecological Benefits of Mutualistic Relationships

Interactions Between Organisms: Parasitism and Commensalism

The Role of Fungi in Plant Relationships

• Fungi assist plants in water and nutrient absorption, but they can become parasitic by demanding carbohydrates from the plant.

• The nature of this interaction can vary based on environmental conditions.

Examples of Commensalism

• A classic example is the remora fish, which attaches to larger fish to feed on leftover food after predation.

• Another instance is the "inquilino" relationship, where one organism benefits from another's protection or transportation without causing harm.

Unique Symbiotic Relationships

• An interesting case involves a crab living within a tube formed by another organism; the crab relies on this structure for shelter while not affecting its host negatively.

• This relationship illustrates how organisms can coexist without direct impact on each other’s survival.

Conclusion and Further Study