Chapter 23 - Population Ecology, Community Ecology, and Biodiversity

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• Crocodiles would consume some of the creatures that graze on seeds and plants on rain forest islands with top predators, decreasing the population of these animals and protecting the number of plant species in these locations.

  • Food availability and the energy it offers organisms influence their reproductive strategy.
  • In response to energy availability, different species employ various reproduction methods.
  • Organisms that dwell in unstable habitats (with limited availability to energy-containing chemicals) will generate a high number of progeny at once.
  • Because there is less availability.

• Individual creatures in populations interact with one another and with their environment in various ways.

  • This chapter examines the variables that influence population growth rates and the biodiversity of the communities in which they dwell.
  • Some populations will ultimately outnumber the resources available in their environment, and their expansion will be stifled.

• Factors that restrict the expansion of these populations might be density-dependent or density-independent.

  • Disease, predation, and competition for food, habitat, or mates are examples of density-dependent variables that restrict population expansion.
  • Temperature, precipitation, and natural catastrophes are examples of density-independent variables (such as forest fires or volcanic eruptions).
  • As a result of these constraints, a population grows logistically.

• @@The reproductive system is influenced by the availability of energy.@@

  • K-selected reproductive techniques are more common in populations that live in more stable conditions and have more energy available.
  • K-selected populations have relatively steady population sizes that are at or near their environment's carrying capacity.
  • K-selected populations typically breed more than once in their lifespan, with few offspring produced each reproductive cycle.
  • K-selected populations provide more parental care to their kids, resulting in better offspring survival rates.
  • Logistic growth occurs in K-selected populations, which are sensitive to density-dependent variables.
  • The majority of mammal and avian species have K-selected populations.

• Populations who live in insecure conditions with limited energy resources have r-selected reproductive methods.

  • These populations breed at a younger age, and in many cases, just once in their lives.
  • Each reproductive cycle gives birth to a significant number of progeny.
  • However, r-selected populations provide little or no parental care to their young, resulting in considerably lower offspring survival rates.
  • r-selected populations go through "boom or bust" cycles, with periods of exponential growth leading to populations that significantly exceed an environment's carrying capacity ("booms"), followed by fast population declines ("busts").

• A community is a collection of interacting populations that share a common environment.

  • The species composition and diversity of communities can be used to describe them.
  • The number of species that dwell in a given region is referred to as its species makeup.
  • The number of species in a region, as well as the number of individuals of each of those species, are reflected in species diversity.

• Species diversity provides a more realistic picture of the diversity of species found in a given location.

  • Interactions and interactions among members of a community are critical for organism existence.
  • Interactions between populations within a community might shift throughout time.
  • These shifting relationships can have an impact on how members of the community gain access to the matter and energy they require to survive.

• The variety of living creatures in an ecosystem is referred to as biodiversity.

  • Biodiversity-rich ecosystems are often more robust and adaptive to environmental changes.
  • Abiotic (nonliving) and biotic (living) elements both influence biodiversity.
  • Climate and water availability, for example, will impact the sorts of species and the quantity of creatures of each species present in an ecosystem.

• The number of consumers that may live in an ecosystem is limited by biotic variables such as the number of producers.

  • The structure of an ecosystem's food chains and food webs will be influenced by its biodiversity.
  • In comparison to their numbers, keystone species have a disproportionately great impact on an ecosystem.

• When wolves were hunted to near-extinction levels in Yellowstone National Park 100 years ago, deer numbers soared.

  • The abundance of deer resulted in a decline in plant diversification.
  • Other animal species that relied on these plant species became extinct.
  • When wolves were reintroduced in the 1990s, they had a significant impact on deer numbers.
  • Other animal and plant species numbers rose, enhancing biodiversity.

• Wolves are an important species.

  • @@Toxins generated by cane toads killed larger creatures that tried to consume them.@@
  • Many native species in Australia have become extinct as a result of cane toads.

• Ecosystems may be disrupted by human actions as well.

  • %%The degradation of habitats (when new towns are developed) might lead to a decline in biodiversity.%%
  • New illnesses may be introduced into the ecosystem when humans move into previously uninhabited areas.
  • When humans relocate to new locations, they may come into touch with previously identified illnesses.
  • Humans also contribute to pollution, which makes water supplies less suitable for other animals.

• ^^Volcanic eruptions, for example, may potentially disturb ecosystems, resulting in changes in biodiversity. Severe weather events, such as hurricanes, can reduce plant and animal productivity.^^

  • Hurricanes and other severe weather events can reduce plant and animal variety in a region. Prolonged droughts can alter an ecosystem's biodiversity.
  • These environmental perturbations can result in population evolution.
  • Environments will favor adaptations that give a competitive advantage.
  • As the environment changes, so will the adaptations that are favored and chosen for.
  • Mutations are responsible for the evolution of adaptations.
  • Mutations are unpredictably occurring phenomena, but selection is not.
  • @@Rapid environmental changes can hasten the rate of evolution.@@

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