APES UNIT 3 EXAM

Life history

is the series of events from birth through reproduction to death.

Life species…how?

shaped by evolution, Operating through natural selection, Adapted for the specific environment

How do life history strategies influence population?

Age of first reproduction, Number of offspring, Amount of parental care given to offspring ,Energy cost of reproduction

K Species

an organism that produces few, high-quality offspring and invests significant energy into parental care to ensure they survive in stable environments. Long lifespans and slow maturation/late sexual maturity. Slow growth. Low death rate, large offspring.

R Species

organisms that prioritize high growth rates, produce many small offspring, and invest minimal energy in parental care. Short lifespans and slow maturation/late sexual maturity. Fast growth. High death rate, small offspring.

Survivorship Curve

a line graph that shows the relative survival rates of a cohort (a group of individuals born at the same time) from birth to the maximum age reached by any member

Type I Survivorship Curve

is a graphical line on an ecology chart showing that most individuals survive through early and middle life before experiencing a sharp increase in mortality/death during old age. It is a convex curve that stays high and flat during youth and middle age, then drops steeply near the end of the maximum lifespan. Parents provide high parental investment and extensive care to protect their young. Species produce very few offspring at one time. These are typical K-selected species which are large in size, live long lives, and mature slowly

Type II Survivorship Curve

represents a population with a constant mortality rate across all ages, meaning individuals have an equal probability of dying at any point in their lifespan. Appears as a steady, straight diagonal line sloping downward from left to right on a logarithmic scale. Age is not a strong predictor of survival; young and old individuals face the same relative daily risk of death from environmental factors. Death is typically driven by constant external threats like random predation, diseases, or accidents. Steady Middle ground.

Type III Survivorship Curve

A concave curve that drops steeply at the start, which representing massive infant/juvenile death and then flattens out for older age classes. Strongly associated with r-selected species, which produce massive numbers of offspring at one time. Involves minimal to no parental care or investment per offspring. Relies on a lottery strategy, even though most newborns die quickly from predation, disease, or harsh conditions, enough absolute numbers survive to adulthood to maintain the population

Carrying Capacity (K)

maximum number of individuals of a specific species that a given environment can support indefinitely without depleting essential resources. max number of individuals in a population that an ecosystem can support based off on limiting resources.

Limiting Factors

any environmental condition or resource that restricts a population's size and stops it from growing infinitely

Density-dependent factors

limiting factors whose effect on a population's growth rate changes depending on the population's density. for example, Infectious illnesses spread much faster and more severely through crowded populations than sparse ones.

Density-independent factors

environmental forces that limit the size of a population regardless of how crowded or dense that population is. A limiting factor that affects birth and death rates in a population equally, whether it contains ten individuals or ten thousand. Wildfires, hurricanes, tornadoes, floods, and volcanic eruptions are examples

Exponential Growth

a rapid, accelerating increase in population size that occurs when resources are unlimited. When plotted on a graph over time, it forms a distinctive J-curve that gets steeper as the population grows larger. The population grows by a fixed percentage or proportion per unit of time, meaning it adds more individuals each generation. Real-world populations cannot sustain thisforever because environmental resources like food, water, and space are finite.

Logistic Growth

population growth that starts off fast, but then slows down and levels off as the population reaches the maximum number of individuals the environment can support. Plots as an S-shaped curve on a graph. The maximum population size that an environment can sustain indefinitely

Population overshoot

occurs when a population temporarily exceeds the carrying capacity of its environment, depleting vital resources and leading to a sharp population crash or dieback

Population dieback

a sharp and sudden drop in population size that occurs when a species overshoots (exceeds) the carrying capacity of its environment

Triangle Shape (Age Structure diagram)

indicates a rapidly growing population.A wide base means there are a lot of children in the pre-reproductive age group. These young individuals will soon enter their reproductive years meaning the total number of births will likely increase over time. It points to high birth rates and high total fertility rates often seen in developing or less-developed countries

Rectangular/House Shape (Age Structure diagram)

that represents a stable population with slow or zero growth. his shape occurs because the pre-reproductive cohort and the reproductive cohort are roughly equal in size. This indicates that the birth rate is just high enough to replace the dying population, but not high enough to expand it. The country has experienced a significant decline in birth rates and maintains low death rates, paired with a high life expectancy.

inverted Triangle Shape (Age Structure diagram)

that represents a declining or shrinking population negative population growth rate. The bottom bars represent the pre-reproductive cohort. A narrow base means that very few children are being born. The upper bars represent the post-reproductive cohort. A wider top means there is a large percentage of older, aging individuals who are living longer due to high life expectancy

Demographic Transition Model (DTM)

a four- or five-stage framework that explains how birth rates and death rates change as a country transitions from a pre-industrial economy to an industrialized and urbanized one

Stage 1 (Demographic Transition Model)

a pre-industrial period characterized by high birth rates and high death rates that roughly balance out, resulting in a low and stable overall population growth rate. Families have many children because of high infant mortality, a reliance on child labor for agriculture, and the lack of modern family planning or contraception. Poor healthcare, limited sanitation, famine, and frequent outbreaks of infectious disease keep life expectancy low. Because births and deaths are both high and frequently fluctuate due to environmental shocks, war, or disease, the total population size remains small and changes very slowly. Societies in this stage rely almost entirely on rural subsistence agriculture or hunting and gathering. 

Stage 2 (Demographic Transition Model)

an early expanding phase marked by a high birth rate and a rapidly falling death rate, which causes a population boom. Birth Rate remains high because cultural norms, agricultural lifestyles, and family traditions still favor large families.Death Rate drops fast due to advances in public health, clean water, sanitation, and medical care (especially pediatric care). Population Growth rises very rapidly because births greatly outnumber deaths. Improvements in food security and nutrition, Expanded access to vaccines and basic medicine, Better personal hygiene and community sanitation

Stage 3 (Demographic Transition Model)

ow death rates and rapidly decreasing birth rates, which causes total population growth to slow down. Birth Rates falling quickly Death Rates Remaining low and stable. Population Growth Continuing to increase, but at a much slower and moderating pace. Economic Phase is Shifting from an industrializing economy to a fully mature urban society. People move from farms to cities. In cities, children cost more to raise and do not work on farms, making large families less practical. Greater access to education and jobs for women leads to delayed marriage and childbearing.c Family planning resources become widely available and culturally accepted. Lower infant mortality means parents no longer need to have extra children to ensure some survive to adulthood

Stage 4 (Demographic Transition Model)

a period where both birth rates and death rates are low, leading to a stable or slow-growing total population. Birth rates drop to low levels, often nearing the replacement level of about 2.1 births per woman. Death rates remain low due to advanced medical care, good sanitation, and stable food supplies. Total population growth is near zero or very slow. People live longer, leading to a higher proportion of older citizens and a larger elderly-to-youth ratio. Advanced industrial and service-based economies reduce the economic need for large families. High levels of education and expanded job opportunities for women often mean people delay having children. Family planning resources and birth control are widely available and commonly used.Most people live in cities rather than rural farming communities, changing the cost and role of raising children