Which birds migrate south for the winter?

Why do birds move from cold places to warm places?

Birds move towards the warmer grounds as a response to change in weather, temperature, wind, habitat for breeding and food availability. It’s a seasonal occurrence, which happens every year at a specific time.

What is the most common spatial distribution among individuals within populations?

The most common spatial distribution among individuals within a population is clumped. Ecological density is a measure of the number of individuals per unit of available living space. The density of a population is usually measured by counting every individual.

When do reproductive barriers arise most quickly in isolated populations?

A. Reproductive barriers will arise most quickly if the isolated populations are very small in number. B. Any division of a species into isolated populations will promote rapid formation of reproductive barriers between them.

How does microevolution occur through natural selection?

In the geographic areas where the populations overlap, natural selection has reinforced color differences that serve as reproductive barriers between the two species The main focus of Charles Darwin’s studies was on the gradual process of adaptation whiten populations. In other words, microevolution occurs by means of natural selection.

What is the relationship between reproductive barriers and speciation?

B. Reproductive barriers can arise only when populations are geographically separated. C. Reproductive barriers can arise in the absence of geographic isolation, but the process of speciation would be slow and take many generations. D. Speciation can occur with even a single gene mutation if that mutation involves reproductive barriers.

What is the distribution of individuals within a population?

Most populations are divided into subpopulations. A uniform distribution of individuals within a population occurs if each individual’s position is independent of others’ positions. The most common spatial distribution among individuals within a population is clumped.

What are the factors that affect spatial distribution?

Spatial Distribution Models. Spatial distribution of individuals belonging to one population or of populations belonging to one metapopulation are affected by resource availability and habitat fragmentation, and are created by natural factors such as dispersal, migration, dispersion, and human-caused factors such as habitat fragmentation.

How does habitat fragmentation affect spatial distribution of populations?

Spatial distribution of individuals belonging to one population or of populations belonging to one metapopulation are affected by resource availability and habitat fragmentation, and are created by natural factors such as dispersal, migration, dispersion, and human-caused factors such as habitat fragmentation.

What is speciation and why is it important?

Speciation, that is, the evolution of reproductive barriers eventually leading to complete isolation, is a crucial process generating biodiversity. Recent work has contributed much to our understanding of how reproductive barriers begin to evolve, and how they are maintained in the face of gene flow.

What are the different types of reproductive barriers?

Behavioral isolation: courtship rituals unique to certain species act as effective, reproductive barriers. Mechanical isolation: morphologic differences can prevent successful mating. Gametic isolation: sperm of one species may not be able to fertilize egg of another species.

Are speciation rates related to reproductive isolation in birds?

For this pair of clades, speciation rates are faster in the clade with faster rates of evolution of reproductive isolation (pheasants: speciation = 0.26 lineages Myr –1; parrots: speciation = 0.22 lineages Myr –1 ). However, across all birds, these quantities appear to be unrelated.

What are the two barriers to speciation?

Speciation: Prezygotic and Postzygotic Barriers. Biological species concept: Defines a species as a population or a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring with members of other populations Reproductive isolation: the existence of biological factors that impede members…

What happens when two populations of birds come together?

When birds from the two populations are brought together, they produce young whose appearance is intermediate between the two parents. These offspring will breed with each other or with birds from either parent population, and all offspring of these pairings appear intermediate to various degrees. What keeps the two population separate?

What is the pattern of distribution among individuals in population?

On large scales, the pattern of distribution among individuals in a population is clumped. On small scales, the pattern may be clumped, regular, or random. Clumped distribution, also called aggregated distribution, clumped dispersion or patchiness, is the most common type of dispersion found in nature.

What is the distribution of a species across its geographic range?

Many species have a patchy distribution of populations across their geographic range. Geographic range includes areas occupied during all life stages. Some species, such as monarch butterflies, migrate long distances between summer and winter habitats.

What factors affect the distribution of species?

Historical Factors Evolutionary history and geologic events affect modern distribution of species. Example: Polar bears evolved from brown bears in the Arctic. They are not found in Antarctica because of an inability to disperse through tropical regions.

How is the distribution of birds changing?

The distribution of birds is constantly changing: some species expand their range; others exhibit an ever-contracting distribution; still others fluctuate, expanding for a while, then declining again. Two major factors influence such changes: human activities and prolonged shifts in climate.

What is the most important effect of fragmentation?

The most obvio us effect of t he process of fragmentation is the removal o f habitat. T his has led many researchers (Robinson et al ., 1995). When ecologists think of fragmen tation, the word invokes mor e than habitat removal: changes the properties of the remaining habitat (van den Berg et al ., 2001). patterns.

What is the main reason for the decline in bird populations?

This decline is due to human activities, such as the cutting down of forests, contamination, invasive species , and human-induced climate change . The world’s tropical forest bird population may be permanently reduced by 144 million individuals per year.

What is population distribution and abundance in ecology?

Ecology: Population Distribution and Abundance. Interactions with populations include sexual reproduction and competition. Abundance can be reported as population size (# of individuals), or density (# of individuals per unit area). Sometimes the total area occupied by a population is not known.

What is a normal distribution in biology?

– type of distribution where the frequency is highest near the middle value and decreases toward each extreme end of the range. – a population has a normal distribution when all phenotypes provide an equal chance of survival. – traits not undergoing natural selection have a normal distribution. – evolution within a population.

Why do individuals within a population have different traits?

Individuals within a population vary in their traits. Figure 2: Relationship between beak depth of offspring and their parents Some of these variable traits are heritable — passed on to offspring. More offspring are produced than can survive because of limited resources such as food and nesting sites.

How does altitude affect bird species distribution and diversity?

Altitude affects bird species distribution and diversity in the mountainous region. Elevation type of the given environment (W aterhouse et al.2002). This is a ffecting the distribution and energy into the ecosystem. Ecological studies show tha t lower altitude has more bird species throughout the altitudes (Jankowski et al.2009).

How does population size affect the distribution of populations?

The spatial distribution of populations changes with population size. Growing populations expand over a larger area as individuals in the high-density core disperse to the fringe of the population or colonize new patches. Declining populations shrink into refuges that maintain isolated demes of a metapopulation.