The concept of population: a collection of the same species or organisms that occupy a specific space within a certain period of time and perform certain functions as part of a biological community

Population spatial distribution characteristics

size and density

birth and death rates

age structure

Sex ratio structure: The ratio of males to females of a certain age in a population. Is an element of population structure that reflects the potential of a population to produce offspring

Discrete growth model of population

Continuous growth model of population: J type

Logistic growth model of population: S-type

The concept of population ecological countermeasures: the “countermeasures” of organisms evolving in different directions in the struggle for survival

r Countermeasures: Small individuals, short lifespan, low survival rate, weak competitiveness, but high value-added rate, the population is prone to sudden fluctuations of ups and downs, and farmland insects, weeds, etc.

K strategy: large individuals, long lifespan, high survival rate, strong competitiveness, stable population density, and always maintained at the maximum environmental capacity. Such as trees, large carnivores, etc.

Application of population ecological countermeasures: Proper allocation of various organisms in r-k type lineages

Seasonal waxing and waning: population numbers of wheat tillers and cotton bugs

inter-annual cyclical fluctuations

Irregular fluctuations: most insects

Population Outbreaks: Pests, Diseases and Rodent Infestations

Population balance: large ungulates, carnivores, red ants, etc.

Population decline and extinction: overgrazing, overhunting, etc.

The concept of ecological invasion: Because humans consciously or unconsciously bring certain organisms into areas suitable for their habitat and reproduction, the population continues to expand, and the distribution area gradually and steadily expands. This process is called ecological invasion.

Case 1: European cave rabbit

Case 2: A yellow flower in Canada

Case 3: Lucky snail

Case 4: Water hyacinth

Causes of population fluctuations

regulation of population fluctuations

positive interaction

negative interaction

allelopathy

The concept and characteristics of community

community species structure

species diversity

spatiotemporal structure of the community

Nutritional structure of the community

Niche concept: the function and status of organisms in species and ecosystems. It reflects the comprehensive adaptation characteristics of organisms to the environment when completing their normal life cycles.

niche theory

Application of ecological niche theory in agriculture

The concept of community succession: as time goes by, some species of biological communities disappear, and other new species appear. The community and its environment move in a certain direction, and there is a sequential development process of change.

community succession type

Top communities and artificial subtops

Causes of community succession

Structural changes in community succession

Functional changes in community succession

Clever use of the law of succession: Using the principle of internal community succession, certain means can be used to transform the environment into a state conducive to production or accelerate the succession process.

The use of nature requires controlled investment: if human interference causes the community to be in an unstable state, to maintain the long-term existence of this unstable community, maintenance capacity must be increased.

Environment-dominant organisms: The characteristics of the top community in an area are restricted by the environment and can only reach a certain level.

The concept of ecological adaptability: a manifestation of specific traits formed by organisms in order to adapt to the environment in the competition for survival. It is the result of the comprehensive effect of various ecological factors in the environment on organisms, and ultimately manifests as ecological adaptation of convergence and divergence.

Convergent adaptation and life forms: Different species of organisms with distant biological relationships show similar ecological characteristics because of the same environment.

Divergent adaptation and ecotype: Different individuals of the same species produce ecological variation due to different environments