It is written in the book that the size of the population is determined by the birth rate, mortality

For example, a population has 10 individuals, 1 is born and 1 dies in a year, and the birth rate: 1 10

Mortality rate: 1 10

The actual birth rate, the death rate is more complex than you assume. If I apply pesticides to the field, the mortality rate of the insects increases, and the population decreases.

Family planning has reduced the birth rate and reduced population density.

When the Three Gorges is built with hydropower and residents move out, the local population decreases, and the population density of the incoming population increases.

The same is the same, look at it separately.

You've miscalculated both rates.

It is not necessarily possible to use them to figure it out.

These are two different concepts.

Birth mortality and migration determine the trend of population size.

Thus determining the size of the population.

Because you miscalculated.

In fact, the birth rate and death rate are relatively viewed, and the migration and emigration are relatively viewed.

The birth rate and mortality rate can be simply understood as: the number of individuals born and died. Look at the inside of a population, so you should be able to do it.

Raise. Example.

Population. body, 1 dead 1

Rate: 1 10

Mortality rate: 1 10

Actual. rate, mortality ratio.

Hypothesis. Complex. False. I.

Farmland. Apply pesticides.

Insect. Mortality increases.

Population size. Decrease.

Plan. Fertility decreases.

Rate. Decreased oral density.

Three Gorges to build hydropower.

Residents moved. Mouth.

Decrease. Immigration.

Mouth. Population density. Increase. See.

It should be that the expansion and contraction of the population is determined by the birth rate and mortality rate, and the migration and emigration.

Based on the calculation of a couple with two children, according to demographers, it will take about 20 40 years for the population of developing countries such as Mexico to double, 40 80 years for the United States, Sweden will have a relatively stable population, and Germany will have a decreasing population. **This dynamic increase or decrease in population is mainly determined by ( ).

a Population size and density b Population age composition c Population sex ratio d Birth rate and mortality rate [Analysis] In the population of higher animals, especially in the human population, the ratio of male to female is roughly the same, and the dynamic ** of a population is obviously determined by the age composition of the population. At present, the age structure of the population in most developing countries is growing rapidly; In the United States, growth has been slow; Germany is in decline, and this growth trend is determined by the age composition of the population. The demographic dynamics** in this question are based on age composition.

Population density refers to the number of populations in the unit area of the current population, birth rate, mortality rate, incoming, and outgoing will directly affect the population at that time, so they will determine the population density, and the age composition has no effect on the population at that time, but only affects the birth rate and mortality rate in the future.

a. Sex ratio can affect population density, a is wrong;

b. The migration rate and the migration rate can determine the population density, and B is wrong;

c. Species richness, community structure and interspecific collision relationships are the characteristics of the community.

d. The density of the population is the most basic quantitative characteristic of the population

Test Topic: Characteristics of Populations Special Topic: Analysis:

Population characteristics include population density, birth and death rates, migration and emigration rates, age composition and sex ratio; Both the birth rate and the mortality rate affect the change in the population size, but the age composition affects the change in the number by affecting the birth rate and the death rate, and the sex ratio affects the change in the number by affecting the birth rate a. The population density directly depends on the size of the birth rate, the mortality rate, the migration rate and the migration rate, a is correct; b. If the sex ratio affects the change in quantity by affecting the birth rate, b is wrong; c. Age composition affects population density by influencing birth rate and mortality rate, c is correct; d. Population characteristics include quantitative characteristics, spatial characteristics and genetic characteristics, d is correct Therefore, it is selected: b Comments: This question examines the relevant knowledge of population characteristics, which is intended to test the candidates' ability to understand the key points of the knowledge they have learned, grasp the internal relationship between knowledge, and form a knowledge network structure

Answer dIn the absence of migration or emigration, the intraspecific struggle is eased, the birth rate is higher than the original, and the mortality rate is smaller than the original, but the absolute value of the birth rate is not necessarily greater than the absolute value of the mortality rate, and it may be smaller than the absolute value of the birth rate.